Procaine in Cardioplegia: Does It Affect the Endothelial Function?

Objective: Cardioplegic solutions are widely used in cardiac surgery and hyperkelemia in cardioplegia has been demonstrated to impair the endothelium‐derived hyperpolarizing factor (EDHF)‐mediated endothelial function. The present study examined the effect of procaine in St. Thomas Hospital Cardioplegia on the EDHF‐mediated response in porcine coronary arteries. Methods: Isometric force study: Porcine coronary micro‐arteries were studied in a myograph. Two rings taken from the same artery (diameter 200–450 μm, n = 8 ) were incubated with Kreb's solution as control or Kreb's solution plus procaine (1 mM) at 37 °C for 1 h, respectively. The EDHF‐mediated relaxation was induced by bradykinin (BK, ?10 ～?6.5 log M) in the presence of indomethacin (Indo, 7 μM), NG‐nitro‐L‐arginine (L‐NNA, 300 μM), and hemoglobin (HbO, 20 μM) after U46619‐precontraction (?8 log M). Electrophysiological study: The membrane potential of a single smooth muscle cell in coronary arteries was measured by a microelectrode after superfusion with Kreb's solution or Kreb's containing procaine (1 mM) for 1  h. Results: Procaine had little effect on the resting force of porcine coronary micro‐arteries (0.94 ± 0.74 mN vs. 0.67 ± 0.23 mN in control, P > 0.05 ) and did not alter the U46619‐induced precontraction (10.7 ± 1.7 mN vs. 12.0 ± 1.7 mN, P > 0.05 ). The BK‐induced, EDHF‐mediated relaxation was increased by the treatment with procaine with the EC50 shifted leftward (97.3 ± 0.6% vs. 83.0 ± 5.1% at ?7 log M and 99.4 ± 0.6% vs. 96.7 ± 1.6% at ?6.5 log M, P < 0.05 ; EC50: ?8.57 ± 0.24 vs. ?7.92 ± 0.23 log M, P < 0.05 ). Procaine slightly depolarized the smooth muscle cell (?56.3 ± 1.0 vs. ?59.3 ± 0.7 mV, P > 0.05 ) and decreased the BK‐induced hyperpolarization from ?70.3 ± 0.4 mV to ?68.0 ± 0.8 mV (?7 log M, P < 0.05) and from ?72.3 ± 0.7 mV to ?68.8 ± 0.8 mV (?6.5 log M, P < 0.01) . Conclusions: In the coronary arteries, procaine has depolarizing effect but it enhances the EDHF‐mediated relaxation. Therefore, addition of procaine in cardioplegia may preserve the EDHF‐mediated endothelial function.     

Impaired EDHF-Mediated Relaxation in Porcine Pulmonary Micro-Arteries by Cold Storage with University of Wisconsin and Euro-Collins Solutions

Background: Vascular endothelium plays a key role in regulation of vascular tone. Hyperkalemia has been demonstrated to impair the EDHF‐mediated endothelial function in coronary circulation. University of Wisconsin (UW) and Eruo‐collins (EC) solutions are used for organ preservation in transplantation surgery. The potassium concentration in UW or EC solutions is as high as 125 mmol/L or 115 mmol/L, respectively. This study was designed to examine whether hyperkalemia or storage with UW and EC solutions affects the relaxation mediated by EDHF in the porcine pulmonary micro‐arteries. Methods: Porcine pulmonary micro‐artery rings (diameter 200–450 μm) were studied in myograph (n = 8 in each group). After incubation with hyperkalemia (K⁺ 125 mmol/L, at 37° C), UW or EC solutions (at 4° C for 4 hours), EDHF‐mediated relaxation induced by bradykinin (BK, ?10 to ?6.5 log M) in the presence of inhibitors for cyclooxygenase (Indomethacin, 7 μM), nitric oxide synthase (N^G‐nitro‐_L‐arginine, 300 μM), and oxyhemoglobin (20 μM) was compared with control (Krebs' solution) in precontraction with U₄₆₆₁₉ (?7.5 log M). Results: The EDHF‐mediated relaxation to BK was 69.6 ± 6.3% compared with 97.1 ± 1.7% (p= 0.003) in control (no inhibitors). After incubation with hyperkalemia, the relaxation significantly decreased (38.6 ± 3.0% vs. 59.1 ± 7.4%, p= 0.03 ). Storage with UW or EC solutions also significantly decreased the relaxation (49.3 ± 7.3% vs. 65.2 ± 3.5%, p= 0.04 and 51.9 ± 8.4% vs. 60.3 ± 6.1%, p= 0.02 , respectively). Conclusions: In porcine pulmonary micro‐arteries, exposure to hyperkalemia or storage with UW or EC solutions at 4°C for 4 hours impairs the EDHF‐mediated endothelial function. The clinical significance of this effect should be further studied.     

Procaine in Cardioplegia: The Effect on EDHF‐Mediated Function in Porcine Coronary Arteries

Abstract Objectives: Hyperkalemia in cardioplegia impairs the endothelium‐derived hyperpolarizing factor (EDHF)‐mediated function. This study examined the effect of procaine in cardioplegia on the EDHF‐mediated response in porcine coronary arteries. Methods: An isometric force study was performed in a myograph. Two rings taken from the same artery (diameter 200–450 μm) were incubated with Krebs solution (group I) or 20 mM K⁺ (group II) with/without procaine (1 mM) at 37°C for 1 hour. The EDHF‐mediated relaxation was induced by bradykinin (BK,‐10 ?‐6.5 log M) after U₄₆₆₁₉ (‐8 log M, in group I) or K⁺‐precontraction (in group II) in the presence of indomethacin (7 μM), N^G‐nitro‐L‐arginine (300 μM), and hemoglobin (20 μM). The membrane potential of a single smooth muscle cell was measured by a microelectrode after superfusion with Krebs solution with/without procaine for 1 hour. Results: The EDHF‐mediated relaxation was increased by the treatment with procaine with the EC₅₀ shifted leftward (97.3 ± 0.6% vs. 83.0 ± 5.1% at‐7 log M and 99.4 ± 0.6% vs. 96.7 ± 1.6% at‐6.5 log M, p < 0.05; EC₅₀.‐8.57 ± 0.24 vs.‐7.92 ± 0.23 log M, p < 0.05). Procaine decreased the BK‐induced hyperpolarization from‐72.3 ± 0.7 mV to‐68.8 ± 0.8 mV (‐6.5 log M, p < 0.01). The EDHF‐mediated relaxation in arteries exposed to 20 mM K⁺ was not altered by procaine (49.9 ± 7.4% vs. 55.8 ± 7.6%, p > 0.05). Conclusions: In the coronary arteries, procaine has a depolarizing effect but it enhances EDHF‐mediated relaxation. Addition of procaine in cardioplegia did not change the EDHF‐mediated endothelial function.     

Epoxyeicosatrienoic acids (EET11,12) may partially restore endothelium-derived hyperpolarizing factor–mediated function in coronary microarteries

Background. Endothelial cells derive nitric oxide, prostacyclin, and endothelium-derived hyperpolarizing factor (EDHF). The cytochrome P-450–monooxygenase metabolites of arachidonic acid (epoxyeicosatrienoic acids [EETs]) have been suggested to be EDHF. This study was designed to examine the effect of EET_11,12 with regard to the possibility of restoring EDHF function when added into hyperkalemic cardioplegic solution.Methods. Porcine coronary microartery rings were studied in a myograph. In groups 1 and 2, paired arteries were incubated in either hyperkalemic solution (K⁺ 20 mmol/L) or Krebs’ solution (control). In group 3, the paired arteries were incubated in hyperkalemia plus EET_11,12 (1 × 10^−6.5 mol/L) or hyperkalemia alone (control) at 37°C for 1 hour, followed by Krebs’ washout and then precontracted with 1 × 10^−8.5 mol/L U46619. The EDHF-mediated relaxation to EET_11,12 (group 1) or bradykinin (groups 2 and 3) was studied in the presence of N^G-nitro-l-arginine, indomethacin, and oxyhemoglobin.Results. After exposure to hyperkalemia, the EDHF-mediated maximal relaxation by bradykinin (72.5% ± 7.8% versus 41.6% ± 10.6%; p < 0.05), but not by EET_11,12 (18.4% ± 3.3% versus 25.1% ± 4.9%; p > 0.05) was significantly reduced. Incubation with EET_11,12 partially restored EDHF function (33.3% ± 9.5% versus 62.0% ± 8.5%; p < 0.05).Conclusions. In coronary microarteries, hyperkalemia impairs EDHF-mediated relaxation, and EET_11,12 may partially mimic the EDHF function. Addition of EET_11,12 into cardioplegic solution may partially restore EDHF-mediated function reduced by exposure to hyperkalemia.     

Endothelium‐Dependent and‐Independent Coronary Relaxation Induced by Urocortin

Abstract Urocortin, a newly identified polypeptide, possesses cardiac effects. However, the underlying mechanism of its coronary action is still unclear. In the present study we investigated the possible role of endothelial nitric oxide and Ba²⁺‐sensitive K⁺ channels in the endothelium‐dependent relaxant response to urocortin in the isolated rat left anterior descending coronary arteries. Changes of vessel tone were measured in microvessel myographs. Urocortin produced both endothelium‐dependent and‐independent relaxation with IC₅₀ of 2.52 nM and 16.5 nM, respectively. Denuation of endothelium decreased the relaxing potency of urocortin. In the endothelium‐intact rings pretreated with 100 μM N^G‐nitro‐L‐arginine methyl ester (L‐NAME) or 10 μM 1H‐[1,2,4]oxadiazolo[4,2‐α]quinoxalin‐1‐one (ODQ), the urocortin‐induced relaxation was similar to that observed in endothelium‐denuded rings. The relaxant response to urocortin was markedly reduced in endothelium‐intact rings precon‐stricted by 35 mM K⁺. Pretreatment with 100 μM BaCI₂ significantly reduced urocortin‐induced relaxation without an effect on the maximum relaxation. Combined treatment with BaCI₂ plus L‐NAME did not produce additive inhibition. In contrast, BaCI₂ did not alter urocortin‐induced relaxation in the endothelium‐denuded rings. In the endothelium‐denuded rings, BaCI₂ at 100 μM also inhibited nitric oxide donor‐induced relaxation. In conclusion, our results suggest that urocortin‐induced endothelium‐dependent relaxation of rat coronary arteries is primarily mediated by endothelial nitric oxide and subsequent activation of Ba²⁺‐sensitive K⁺ channels. The urocortin‐induced endothelium‐dependent relaxation appears to be cyclic GMP‐dependent.     

Nitric Oxide and Endothelium‐Derived Hyperpolarizing Factor in Human Arteries and Veins

Abstract Background: We have investigated and compared nitric oxide (NO) release and endothelium‐derived hyperpolarizing factor (EDHF)‐mediated hyperpolarization in the human internal mammary artery (IMA), radial artery (RA), saphenous vein (SV), and coronary artery. Materials and Methods: Vessel segments taken from coronary artery bypass grafting or heart transplantation patients were placed in an organ chamber. NO‐sensitive electrode or intracellular glass microelectrode was used to study NO or EDHF in response to acetylcholine (ACh) and bradykinin (BK). Results: The resting membrane potential of the smooth muscle cells of IMA, RA, and SV was‐58 ± 0.84 (n # 61),‐61 ± 1.3mV (n # 46, p # 0.03), and‐62 ± 0.9 mV (n # 23, p = 0.0001) respectively. BK‐(10–⁷M) induced EDHF‐mediated hyperpolarization (‐10.9 ± 1.5 mV, n # 7) in the IMA was significantly greater than that in RA (‐5.8 ± 0.9 mV, n # 6, p # 0.04) and SV (‐5.1 ± 0.5 mV, n = 8, p < 0.01). The basal release of NO in IMA (16.8 ± 1.9 nM) was significantly higher than that in RA (11.1 ± 1.0 nM, n # 12, p # 0.02) and in SV (9.9 ± 2.8 nM, n # 13, p < 0.001). The stimulated release of NO to BK in IMA was significantly greater than that in RA (44.3 ± 4.0 vs 25.8 ± 3.6 nM, n # 8, p # 0.004). The duration of NO release was longer in IMA than in RA or in SV. Conclusions: The basal and stimulated release of NO and EDHF‐mediated hyperpolarization in the IMA are significantly greater than that in the RA and SV. EDHF exists in all these human vessels. This study reveals the differences among human vessels regarding the endothelial function that have implications in vasospasm, coronary protection, or long‐term graft patency.     

Procaine in cardioplegia: the effect on EDHF-mediated function in porcine coronary arteries

OBJECTIVES: Hyperkalemia in cardioplegia impairs the endothelium-derived hyperpolarizing factor (EDHF)-mediated function. This study examined the effect of procaine in cardioplegia on the EDHF-mediated response in porcine coronary arteries. METHODS: An isometric force study was performed in a myograph. Two rings taken from the same artery (diameter 200-450 microm) were incubated with Krebs solution (group I) or 20 mM K+ (group II) with/without procaine (1 mM) at 37 degrees C for 1 hour. The EDHF-mediated relaxation was induced by bradykinin (BK, -10 approximately -6.5 log M) after U46619 (-8 log M, in group I) or K+-precontraction (in group II) in the presence of indomethacin (7 microM), NG-nitro-L-arginine (300 microM), and hemoglobin (20 microM). The membrane potential of a single smooth muscle cell was measured by a microelectrode after superfusion with Krebs solution with/without procaine for 1 hour. RESULTS: The EDHF-mediated relaxation was increased by the treatment with procaine with the EC50 shifted leftward (97.3 +/- 0.6% vs. 83.0 +/- 5.1% at -7 log M and 99.4 +/- 0.6% vs. 96.7 +/- 1.6% at -6.5 log M, p < 0.05; EC50: -8.57 +/- 0.24 vs. -7.92 +/- 0.23 log M, p < 0.05). Procaine decreased the BK-induced hyperpolarization from -72.3 +/- 0.7 mV to -68.8 +/- 0.8 mV (-6.5 log M, p < 0.01). The EDHF-mediated relaxation in arteries exposed to 20 mM K+ was not altered by procaine (49.9 +/- 7.4% vs. 55.8 +/- 7.6%, p > 0.05). CONCLUSIONS: In the coronary arteries, procaine has a depolarizing effect but it enhances EDHF-mediated relaxation. Addition of procaine in cardioplegia did not change the EDHF-mediated endothelial function.     

Effect of 11,12-epoxyeicosatrienoic acid as an additive to St. Thomas' cardioplegia and University of Wisconsin solutions on endothelium-derived hyperpolarizing factor-mediated function in coronary microarteries: influence of temperature and time

BACKGROUND: We examined the effect of 11,12-epoxyeicosatrienoic acid (EET(11,12)) added to St. Thomas' Hospital (ST) solution or University of Wisconsin (UW) solution on endothelium-derived hyperpolarizing factor (EDHF)-mediated relaxation under clinically relevant temperature and exposure time. METHODS: Porcine coronary microarteries (200 to 450 microm) were incubated with Krebs' solution (control), ST with or without EET(11,12) (300 nmol/L) at 22 degrees C for 1 hour as well as at 4 degrees C for 1 or 4 hours, and UW with or without EET(11,12) at 4 degrees C for 4 hours. The EDHF-mediated relaxation was induced by bradykinin (-10 to approximately -6.5 log M) in the precontraction evoked by U(46619) (10 nmol/L) or U(46619) (1 nmol/L) plus endothelin-1 (6 nmol/L). RESULTS: The EDHF-mediated relaxation was reduced after exposure to UW (79.7% +/- 4.6% versus 93.6% +/- 2.8%, p = 0.01) at 4 degrees C for 4 hours. One-hour exposure to ST under 22 degrees C or 4 degrees C decreased the relaxation (75.2% +/- 7.6% versus 96.7% +/- 1.6%, p < 0.05) or the sensitivity to bradykinin (-8.04 +/- 0.15 versus -8.50 +/- 0.20 log M, p < 0.05). The relaxation increased to 86.8% +/- 5.3% by addition of EET(11,12) to ST (1 hour at 22 degrees C, p < 0.05) but was unchanged when added to either ST or UW at 4 degrees C for 1 or 4 hours. CONCLUSIONS: As an additive to ST solution, EET(11,12) may partially restore EDHF-mediated endothelial function under moderate hypothermia but had no significant effect under profound hypothermia when added to either ST or UW solution. Further investigation is necessary to improve the effect.     

Epoxyeicosatrienoic acids (EET(11,12)) may partially restore endothelium-derived hyperpolarizing factor-mediated function in coronary microarteries.

Background. Endothelial cells derive nitric oxide, prostacyclin, and endothelium-derived hyperpolarizing factor (EDHF). The cytochrome P-450–monooxygenase metabolites of arachidonic acid (epoxyeicosatrienoic acids [EETs]) have been suggested to be EDHF. This study was designed to examine the effect of EET_11,12 with regard to the possibility of restoring EDHF function when added into hyperkalemic cardioplegic solution.

Methods. Porcine coronary microartery rings were studied in a myograph. In groups 1 and 2, paired arteries were incubated in either hyperkalemic solution (K⁺ 20 mmol/L) or Krebs’ solution (control). In group 3, the paired arteries were incubated in hyperkalemia plus EET_11,12 (1 × 10^−6.5 mol/L) or hyperkalemia alone (control) at 37°C for 1 hour, followed by Krebs’ washout and then precontracted with 1 × 10^−8.5 mol/L U46619. The EDHF-mediated relaxation to EET_11,12 (group 1) or bradykinin (groups 2 and 3) was studied in the presence of N^G-nitro-l-arginine, indomethacin, and oxyhemoglobin.

Results. After exposure to hyperkalemia, the EDHF-mediated maximal relaxation by bradykinin (72.5% ± 7.8% versus 41.6% ± 10.6%; p < 0.05), but not by EET_11,12 (18.4% ± 3.3% versus 25.1% ± 4.9%; p > 0.05) was significantly reduced. Incubation with EET_11,12 partially restored EDHF function (33.3% ± 9.5% versus 62.0% ± 8.5%; p < 0.05).

Conclusions. In coronary microarteries, hyperkalemia impairs EDHF-mediated relaxation, and EET_11,12 may partially mimic the EDHF function. Addition of EET_11,12 into cardioplegic solution may partially restore EDHF-mediated function reduced by exposure to hyperkalemia.     

Histidine-tryptophan-ketoglutarate solution maximally preserves endothelium-derived hyperpolarizing factor-mediated function during heart preservation: comparison with University of Wisconsin solution.

BACKGROUND: The University of Wisconsin (UW) solution is used widely in heart preservation but has been demonstrated to be detrimental to the endothelial function. The present study compares the effect of histidine-tryptophan-ketoglutarate (HTK) and UW solutions on endothelium-derived hyperpolarizing factor (EDHF)-mediated function in porcine small coronary arteries. METHODS: An isometric force study was performed in a myograph and the membrane potential of a single smooth muscle cell was measured electrophysiologically. Small coronary arteries (diameter 457 +/- 15 microm) were incubated with UW (n = 8), HTK (n = 7) or Krebs solution (n = 15) at 4 degrees C for 4 hours. After washout, in the presence of indomethacin (Indo; 7 micromol/liter), N(G)-nitro-l-arginine (l-NNA; 300 micromol/liter) and oxyhemoglobin (HbO; 20 micromol/liter), bradykinin (BK; -10 to -6.5 log M)-induced relaxation was compared in U46619 (-8 log M) pre-contraction. EDHF-mediated hyperpolarization was elicited by BK (-6.5 log M) in the presence of Indo, l-NNA and HbO. RESULTS: BK-induced, EDHF-mediated relaxation was reduced from 93.6 +/- 2.8% to 79.7 +/- 4.6% after UW preservation (p = 0.01 by unpaired t-test and p = 0.005 by 2-way analysis of variance [ANOVA]), whereas HTK incubation did not decrease EDHF-mediated relaxation (87.0 +/- 6.5%, p = 0.3 by unpaired t-test and p = 0.6 by 2-way ANOVA, compared with control, and p = 0.001 by 2-way ANOVA, compared with UW). EDHF-mediated hyperpolarization (10.3 +/- 1.6 mV) was attenuated by UW exposure (3.4 +/- 0.6 mV, [p = 0.002] vs control), but not by HTK exposure (8.3 +/- 1.1 mV, [p = 0.3] vs control). CONCLUSIONS: HTK is superior to UW solution in protecting EDHF-mediated endothelial function in porcine small coronary arteries. The present findings supports the use of HTK solution in heart preservation.     

Circulating Homocysteine and Copper Following Coronary Artery Bypass Graft Surgery with and Without Cardiopulmonary Bypass

Mast cells are thought of primarily in the context of allergic disorders and certain acute inflammatory responses. Recent studies suggest, however, that mast cells are also implicated in the expression of a wide variety of biologic responses such as pulmonary vascular disease. In this study, we evaluated the pulmonary arterial relaxation effect, in vitro, of histamine and the receptor subtype(s) involved in the normotensive Wistar‐Kyoto (WKY) and age‐matched Spontaneously hypertensive rats (SHR) (male, age: 14–22 weeks). Isometric tension change of phenylephrine (1 μM) pre‐contracted pulmonary artery in response to histamine and histaminergic agonists challenge was recorded and compared. Histamine (with 10 μM SKF 91488, a histamine N‐methyl‐transferase inhibitor) caused a concentration‐dependent relaxation (endothelium‐dependent and ‐independent) of both strains of rats. However, the magnitude of relaxation response observed in SHR was smaller and it is corresponded to a diminished H₁‐receptor‐mediated (competitively inhibited by diphenhydramine), endothelium‐dependent (L‐NAME (20 μM)‐sensitive) relaxation. The endothelium‐independent (H₂‐ and H₃‐receptors, suppressed by cimetidine and clobenpropit respectively) component was indistinguishable between both strains of rats. Unlike histamine, dimaprit (a H2‐receptor agonist) consistently produced a similar degree of relaxation in the WKY and SHR. Under the SKF 91488‐free or clobenpropit (1 nM, a H3‐receptor blocker)‐containing conditions, histamine‐evoked relaxation was significantly enhanced in both the WKY and SHR. No potentiation was observed with tetrodotoxin (100 nM) present. Imetit (a H3‐receptor agonist) failed to produce relaxation and a further contraction was observed in both strains of rats. The magnitude of imetit‐induced contraction was greater in the WKY than in SHR. Imetit‐evoked contraction was reduced in he presence of tetrodotoxin (100 nM) and clobenpropit (3 nM). Application of SQ 22536 (100 μM), L‐NAME (50 μM), ouabain (10 μM), iberiotoxin (100 nM), glibenclamide (3 μM) and apamin (500 nM) failed to modify the endothelium‐independent relaxation of histamine. A supplementation of L‐arginine (500 μM) significantly potentiated histamine‐evoked relaxation in the WKY and SHR. In conclusion, multiple histaminergic (H1‐, H2‐ and H3‐) receptors are present in rat pulmonary artery. A reduced histamine‐induced relaxation in SHR is due to the diminished H1‐receptor‐mediated, endothelium‐dependent relaxation. The endothelium‐independent (H2‐ and H3‐receptors) component of histamine‐induced relaxation, however, was not modified by hypertension.     

Comparison of University of Wisconsin and St Thomas' Hospital solutions on endothelium-derived hyperpolarizing factor-mediated function in coronary micro-arteries

BACKGROUND: It is controversial whether coronary endothelial function is impaired after cold exposure to University of Wisconsin (UW) or St. Thomas' Hospital (ST) solution during heart transplantation. We therefore examined the effects of cold storage of coronary micro-arteries with UW or ST solution on endothelium-derived hyperpolarizing factor (EDHF)-mediated function. METHODS: Porcine and human coronary arteries were immersed in either UW or ST solution at 4 degrees C for 4 hr and then normalized in a wire myograph. RESULTS: In the rings (normalized diameter: 200-500 microM) precontracted by U46619, EDHF-mediated relaxation and hyperpolarization were initiated by bradykinin (BK) or A23187 in the presence of indomethacin and NG-nitro-L-arginine. In the human coronary arteries, the EDHF-mediated relaxation to BK was reduced by UW solution from 53.2+/-5.6% to 24.0+/-2.7% (P=0.006). The reduced EDHF-mediated relaxation occurred concurrently with the decreased hyperpolarization to BK (17.0+/-1.5 vs. 10.5+/-1.1 mV, n=10, P=0.004) or A23187 in porcine coronary arteries. In the control arteries, K+ channel blockers, either glybenclamide or tetraethylammonium reduced the EDHF-mediated relaxation. After exposure to UW solution, the EDHF-mediated relaxation was further significantly inhibited. In contrast, ST solution did not affect these responses. CONCLUSIONS: These results show that in coronary micro-arteries, UW, but not ST, solution impairs the EDHF-mediated function and inhibits the Ca2+-activated and ATP-sensitive K+ channels. Our comparative study suggests that ST solution may be superior to UW solution in preserving the EDHF-related endothelial function of coronary micro-arteries.     

Pituitary adenylate cyclase activating peptides relax human pulmonary arteries by opening of KATP and KCa channels

BACKGROUND—Pituitaryadenylate cyclase activating peptides (PACAPs) are potent endotheliumindependent dilators of human coronary arteries; however, their effectson human pulmonary arteries are unknown.
Methods—Thevasorelaxant effects of PACAP27 on human pulmonary segmental arterieswere studied and the specific potassium (K⁺) channelregulatory mechanisms in the vasorelaxant effects were tested by meansof isometric contraction experiments.
RESULTS—PACAP27produced dose dependent relaxations of 10 µM rings preconstrictedwith prostaglandin F_2α (PGF_2α ) with half maximal relaxation (IC₅₀) at 17 nM. Pretreatment of thevessels with the ATP sensitive K⁺ (K_ATP)channel blocker glibenclamide (1 µM) or with the Ca²⁺activated K⁺ (K_Ca) channel blockeriberiotoxin (100 nM) inhibited the PACAP27 induced relaxation.
Conclusions—Theseresults provide evidence that PACAPs are potent vasodilators of humanpulmonary arteries and that this relaxation might be mediated byopening of K_ATP and K_Ca channels.

     

The role of magnesium in the endothelial dysfunction caused by global ischemia followed by reperfusion: in vitro study of canine coronary arteries

Objective—To study the role of magnesium in the endothelial dysfunction of canine coronary arteries caused by cardiopulmonary bypass (CPB) global ischemia followed by reperfusion.

Design—Segments of canine coronary arteries were suspended in organ chambers to measure isometric contraction by prostaglandin F _2α , and relaxed by acetylcholine (ACh), sodium fluoride (NaF), calcium ionophore (A ₂₃₁₈₇ ) and sodium nitroprusside (SNP) in crescent concentrations. The investigation protocol had groups with six dogs: CONTROL group (without CPB), CPB group (105?min of CPB without aortic cross‐clamping), ISCH group (45?min of CPB with aortic cross‐clamping), ISCH/REP group (45?min of aortic cross‐clamping followed by 60?min of reperfusion). The coronary relaxations were evaluated with (phase I), without (phase II) and restored magnesium (phase III) to the organ bath.

Results—The presence of magnesium in the organ bath was associated with the greater relaxation in response to agonists of the nitric oxide production. The removal of magnesium from the organ bath was associated with the reduction in the intensity of vessel relaxation. The magnesium restoration to the organ bath was associated with the additional reduction in the intensity of relaxation with the exception of NaF that allowed re‐acquisition of the relaxation observed in the presence of magnesium.

Conclusion—This in vitro study demonstrates that magnesium ion favorably influences the nitric oxide production by the coronary endothelium, attenuating the endothelial dysfunction caused by global ischemia followed by reperfusion.     

Cellular electrophysiological and mechanical effects of celsior solution on endothelial function in resistance coronary arteries

BACKGROUND: We investigated a relatively new organ preservation (Celsior) solution regarding its effect on the endothelium-derived hyperpolarizing factor (EDHF)-mediated function with comparison to St. Thomas Hospital (ST) solution. METHODS: The EDHF-mediated relaxation was induced by bradykinin (BK, -10 to -6.5 logM) in the presence of inhibitors of nitric oxide and prostacyclin in porcine small resistance coronary arteries, before and after incubation in ST (Group Ia, n=11), Celsior (Group Ib, n=13), or Krebs (Group Ic, control, n=12) at 4 degrees C for 4 hr. The EDHF-mediated hyperpolarization of the membrane potential of smooth muscle cells was measured by microelectrode with simultaneous relaxation after cold storage in ST (IIa, n=7), Celsior (IIb, n=6), or Krebs (IIc, control, n=6), or followed by washout with Krebs (ST: IIIa, n=6, Celsior: IIIb, n=6). RESULTS: The EDHF-mediated relaxation was significantly decreased in Group Ia (56.4+/-7.2% vs. 71.2+/-5.3%, P<0.05) and Ib (44.8+/-4.9% vs. 74.7+/-3.3%, P<0.05) but not in Ic. The sensitivity to BK was also significantly decreased (Ia: -7.51+/-0.14 vs. -7.76+/-0.12 log M, P<0.05; Ib: -7.36+/-0.09 vs. -7.60+/-0.09 logM, P<0.05). The resting membrane potential was depolarized in IIa (-44.3+/-1.9 mV, n=7, P<0.05) and IIb (-33.0+/-2.2 mV, n=6, P<0.05) compared with IIc (-57.1+/-1.5 mV, n=6). The EDHF-mediated hyperpolarization decreased significantly in IIa and IIb (3.4+/-0.3 and 3.0+/-0.2 vs. 6.3+/-0.5 mV, P<0.05) and partially restored in IIIa (5.0+/-0.2 vs. 3.4+/-0.3 mV, P<0.05) and IIIb (4.1+/-0.3 vs. 3.0+/-0.2 mV, P<0.05). CONCLUSIONS: Storage with Celsior and ST solutions reduces the EDHF-mediated endothelial function (hyperpolarization and associated relaxation) in porcine small resistance coronary arteries.     

Isoflurane inhibits endothelium-mediated nitric oxide relaxing pathways in the isolated perfused rabbit lung

Purpose

The role of volatile anaesthetics on nitric oxide (NO)-dependent relaxation is unclear in the pulmonary circulation. We examined the effects of isoflurane on NO-dependent relaxation in isolated perfused rabbit lungs.

Methods

Eighteen rabbit lungs were perfused in a constant-flow recirculation manner. In study I (n= 12), acetylcholme (ACh, 4 × 10^?10 ? 10^?8 M) or nitroglycenne (NTG, 6 × 10^?10?10^?8 M) was cumulatively injected into the pulmonary artery in the absence or presence of isoflurane (1, 2 MAC). In study 2 (n=6), ACh was injected as in study I in the presence or absence of Nω-nitro-L-arginine methyl ester (L-NAME, 100 μM), an NO synthesis blocker. In all experiments, indomethacin was administered to prevent formation of vasoactive prostanoid metabolites, and the pulmonary vessels were preconstricted with prostaglandin F2α (PGF2α) infused before ACh or NTG injection. The ACh-or NTG-induced relaxation was expressed as % decrease in PGF2α preconstriction.

Results

Isoflurane at 2 MAC attenuated the dose-dependent relaxation to ACh at doses of 4 × 10^?9 M and 4 × 10^?8 M from 27.8 ± 4.3% and 38.8 ± 5.3% to 17.0 ± 3.5% and 25.5 ± 4.9%, respectively (P < 0.05). Isoflurane did not change the dose-dependent relaxation to NTG and L-NAME abolished the ACh-induced relaxation.

Conclusion

Isoflurane inhibited NO-dependent relaxation in the pulmonary circulation at a site distal to the endothelial cell receptor-mediated responses but proximal to guanylate cyclase activation of vascular smooth muscle. Acetylcholine-induced relaxation in isolated perfused rabbit lungs was regulated primarily by NO.     

The muscarinic receptor antagonist propiverine exhibits α(1)-adrenoceptor antagonism in human prostate and porcine trigonum

Purpose

Combination therapy of male lower urinary tract symptoms with ??₁-adrenoceptor and muscarinic receptor antagonists attracts increasing interest. Propiverine is a muscarinic receptor antagonist possessing additional properties, i.e., block of L-type Ca²⁺ channels. Here, we have investigated whether propiverine and its metabolites can additionally antagonize ??₁-adrenoceptors.

Methods

Human prostate and porcine trigone muscle strips were used to explore inhibition of ??₁-adrenoceptor-mediated contractile responses. Chinese hamster ovary (CHO) cells expressing cloned human ??₁-adrenoceptors were used to determine direct interactions with the receptor in radioligand binding and intracellular Ca²⁺ elevation assays.

Results

Propiverine concentration-dependently reversed contraction of human prostate pre-contracted with 10???M phenylephrine (?log IC₅₀ [M] 4.43?±?0.08). Similar inhibition was observed in porcine trigone (?log IC₅₀ 5.01?±?0.05), and in additional experiments consisted mainly of reduced maximum phenylephrine responses. At concentrations ??1???M, the propiverine metabolite M-14 also relaxed phenylephrine pre-contracted trigone strips, whereas metabolites M-5 and M-6 were ineffective. In radioligand binding experiments, propiverine and M-14 exhibited similar affinity for the three ??₁-adrenoceptor subtypes with ?log?K _i [M] values ranging from 4.72 to 4.94, whereas the M-5 and M-6 did not affect [³H]-prazosin binding. In CHO cells, propiverine inhibited ??₁-adrenoceptor-mediated Ca²⁺ elevations with similar potency as radioligand binding, again mainly by reducing maximum responses.

Conclusions

In contrast to other muscarinic receptor antagonists, propiverine exerts additional L-type Ca²⁺-channel blocking and ??₁-adrenoceptor antagonist effects. It remains to be determined clinically, how these additional properties contribute to the clinical effects of propiverine, particularly in male voiding dysfunction.     

Cyclosporin‐induced endothelial dysfunction and hypertension: are nitric oxide system abnormality and oxidative stress involved?

Abstract Hypertension is a major side effect of cyclosporin (CsA). While the mechanism(s) responsible are unclear, CsA‐induced endothelial dysfunction and CsA‐induced hypertension have been attributed to the CsA effect on the endothelial‐derived factors controlling vasomotor tone. Endothelial nitric oxide (NO) is crucial in the maintenance of a state of basal vasodilation, and recent studies have suggested an NO‐mediated counterregulatory mechanism protective from CsA‐induced vasoconstriction. Our study evaluates endothelial nitric oxide synthase (ecNOS) gene status (PCR analysis) and plasma levels of NO metabolites (ELISA) in kidney and heart transplant patients under chronic CsA treatment with CsA‐induced hypertension. Since CsA increases superoxide production, which metabolises NO, plasma hydroperoxides from cholesterol esters and from triglycerides and peroxynitrite were also evaluated (HPLC) as an index of the presence of superoxides and of “oxidative stress”. Quantification of monocyte ecNOS mRNA and NO metabolites plasma levels from patients and controls (C) demonstrated NO system upregulation in patients notwithstanding the hypertension. The mean ecNOS to β‐actin ratio was 1.80 ± 0.85 in patients vs 0.40 ± 0.09 in C (P < 0.04). NO metabolites were 34.03 ± 14.32 μM in patients vs 11.53 ± 5.64 μM in C (P < 0.001). Hydroperoxides from cholesterol esters and from triglycerides were also increased in patients, 3.4 ± 1.4 vs 1.3 ± 0.6 integrated area units (i. a. u.), P < 0.007 and 10.6 ± 6.4 vs 1.3 ± 0.8 i.a.u., P < 0.008, respectively, as well as the peroxynitrite plasma level, 0.32 ± 0.11 μM/l vs undetectable in C. This study confirms a CsA‐induced NO system upregulation in transplanted patients. However, the NO‐mediated counterregulatory system to CsA‐induced vasoconstriction, present in normals, could be canceled in patients by CsA‐induced superoxide (O₂^?) and free radical production which, by increasing NO metabolism, could contribute to CsA‐induced vasoconstriction and hypertension and predispose to atherosclerosis.     

Arterial Switch Operation with Coronary Arteries from a Single Sinus in Infants

Abstract Background: The implantation of a coronary artery (CA) is critical for the arterial switch operation (ASO) done to treat complete transposition of the great arteries (TGA). Coronary artery abnormalities are risk factors for both early and late mortality after surgery. In this study, the methodology and effects of ASO surgery with coronary arteries from a single sinus were evaluated. Methods and Results: From March 1999 to June 2006, 31 patients were treated with ASO with coronary arteries from a single sinus in our hospital. They aged 11 hours ? 16 months (2.8 ± 3.9 months) and weighted 2.3 ?7.8Kg (3.1 ± 2.5Kg). 27 cases had TGA and a ventricular septal defect (VSD), and 4 had TGA and an intact ventricular septum (IVS). During surgery, a CA button was implanted in the new proximal aorta with “trapdoor” technique or by inverting 90 degrees dorsally; pericardium or arterial augmentation was implanted at the base of the new major artery. The mortality rate after surgery was 25.8%. After 2‐5 years of follow‐up, 2 cases with residual shunting recovered spontaneously, 2 cases had residual pulmonary artery obstruction (30‐56 mmHg), and none of the patients had any significant changes in myocardial ischemia. Conclusion: The implantation of an abnormal coronary artery is practical and feasible; it can reduce both the occurrence of twisting and deforming in the coronary artery after implantation, as well as myocardial ischemia after surgery. Thus, this could improve the surgical success and cure rates.     

Ginsenoside Rb1 blocks Homocysteine-induced endothelial dysfunction

Background. Homocysteine (HCY) is an independent risk factor for atherosclerosis. This study is to investigate the effect of ginsenoside Rb1, a major constituent of ginseng, on HCY-induced endothelial dysfunction and molecular changes in porcine coronary arteries. Methods. Coronary arteries were harvested from pig hearts and cut into 5-mm rings, which were divided into 6 groups including control, HCY alone (50 μM), low-dosed (1 μM), or high-dose (10 μM) Rb1 alone, and HCY plus low-dose or high-dose Rb1. After 24 h incubation, the rings were analyzed for vasomotor function in response to U46619, bradykinin, and sodium nitroprusside (SNP), respectively. In addition, superoxide anion was assessed by lucigenin-enhanced chemiluminescence analysis. Endothelial nitric oxide synthase (eNOS) expression was studied by real-time RT-PCR and Western blot. Results. Endothelium-dependent relaxation (bradykinin) was significantly reduced in rings treated with HCY alone as compared to the control (49.80% versus 71.77%, n = 8, P < 0.05), while either high-dose or low-dose Rb1 alone did not affect endothelium-dependent relaxation. Low-dose Rb1-HCY combined group had partially improved endothelium-dependent relaxation (54.44%), while high-dose Rb1-HCY combined group showed complete recovery of endothelium-dependent relaxation (72.89%). There was no substantial difference in maximal contraction induced by U46619 or endothelium-independent relaxation by SNP among all groups (P > 0.05). Moreover, superoxide anion was markedly increased by 137% in HCY-treated group as compared to the control, but there was no significant changes from the control in all other groups (P > 0.05). Last, eNOS mRNA and protein levels were substantially reduced in HCY-treated group, but not in Rb1-HCY combined groups. Conclusions. This is the first study to demonstrate that ginsenoside Rb1 can effectively block HCY-induced endothelial dysfunction and superoxide anion production as well as eNOS down regulation in porcine coronary arteries. This study suggests that ginseng and its active constituents may have potential clinical applications in controlling HCY-associated vascular injuries.