Effects of cooling and warming on 5-hydroxytryptamine- and acetylcholine-induced contractions of human umbilical vessels: role of nitric oxide

The effects of cooling (to 28 degrees C) and warming (to 41 degrees C) on the vasoconstrictions induced by 5-hydroxytryptamine (5-HT) and acetylcholine (ACh) and the role of nitric oxide in these effects were analyzed in human umbilical artery and vein. 5-HT (10(-9)-10(-4) M) and ACh (10(-9)-10(-4) M) induced concentration-dependent contractions at 37, 28 and 41 degrees C. During cooling, the sensitivity, but not the maximal response, of 5-HT and ACh was significantly higher than at 37 degrees C; and during warming, again the sensitivity, but not the maximal response, of both contractile agents was significantly lower than at 37 degrees C. Neither cooling to 28 degrees C nor warming to 41 degrees C, after treatment with N(G)-nitro-L-arginine methyl esther (L-NAME, 10(-4) M), modify the effect of temperature in both vessels. These results suggest that cooling- and warming-induced responses in human umbilical artery and vein are independent of nitric oxide.     

Role of the nitric oxide on diazoxide-induced relaxation of the calf cardiac vein and coronary artery during cooling

The effects of cooling (to 28 °C) on the vasodilation induced by diazoxide (10⁻⁹–3 × 10⁻⁴  m ) on carbachol-pre-contracted calf cardiac vein and coronary artery and the role of nitric oxide in these effects were analyzed. Diazoxide produced concentration-dependent relaxation of calf cardiac vein and coronary artery rings pre-contracted with carbachol (10⁻⁶  m ). During cooling, the pIC₅₀ values, but not the maximal responses, to diazoxide were significantly lower than at 37 °C in both preparations. Cooling to 28 °C in the presence of N^G-nitro-L-arginine methyl ester (10⁻⁴  m ) did not modify the effect of temperature both in cardiac vein and coronary artery. These results suggest that cooling-induced changes of diazoxide in calf cardiac vein and coronary artery are independent of nitric oxide.     

Role of the endothelium on the response to adrenoceptor agonists of rabbit aorta during cooling

The role of the endothelium in the effects of cooling on the response to alpha1- and alpha2-adrenoceptor agonists of rabbit aorta was studied. The contractions induced by clonidine (10(-9)-3 x 10(-4) M) and xylazine (10(-7)-10(-3) M) but not phenylephrine (10(-9)-3 x 10(-4) M) and methoxamine (10(-9)-3 x 10(-4) M) were enhanced in endothelium-denuded or N(G)-nitro-L arginine methyl- ester (L-NAME) (10(-5) M) pretreated rabbit aorta. The sensitivity, but not the maximal response, of both alpha1- and alpha2-adrenoceptor agonists was significantly lower at 28 degrees C (cooling) than at 37 degrees C. Endothelium removal did not affect the action of cooling. These results were taken as evidence for the specificity of alpha2-adrenoceptor agonists on the production and release of nitric oxide from vascular endothelium. The results suggest that the endothelium seems to have no role in the cooling-induced responses of both alpha1- and alpha2-adrenoceptors.     

Characteristics of ca influxes through voltage- and receptor-operated Ca channels in uterine smooth muscle

The characteristics of Ca channels in isolated uterine smooth muscles from estradiol-treated ovariectomized rats were investigated. When the muscles were preincubated in Ca-depleted Ringer's solution for about 60 min and then immersed in Ca-depleted high K Ringer's solution or treated with acetylcholine (ACh) and serotonin (5-HT), no contractile response was observed. However, in both cases when CaCl2 was then added, a contractile response was induced. The contractile responses induced by KCl, ACh and 5-HT were inhibited dose-dependently by Ca antagonists and these inhibitions were counteracted competitively by an increase in the concentration of CaCl2. The characteristics of KCl-, ACh- and 5-HT-stimulated 45Ca uptake were investigated under the same conditions as the contractile responses. Results indicated that the contractile responses to high KCl, ACh and 5-HT induced by addition of CaCl2 in Ca-depleted Ringer's solution were dependent upon influx of Ca ions into uterine smooth muscle cells.     

Uric Acid: CHARACTERIZATION OF ITS INTERACTION WITH HUMAN SERUM ALBUMIN

Binding of sodium urate to human serum albumin (HSA) was measured by continuous ultrafiltration at pH 7.4 and ionic strength 0.16 over the concentration range 1-13 mg/100 ml. The percent sodium urate bound to 5 g/100 ml HSA was constant over this concentration range: 30.3 (SE+/-0.6)% being bound at 4 degrees C, 22.6+/-0.3% at 22.5 degrees C, and 19.6+/-0.3% at 37 degrees C. Derived association constants, assuming one binding site were 6.0 x 10(2) M(-1) (4 degrees C), 4.47 x 10(2) M(-1) (22.5 degrees C), and 3.88 x 10(2) M(-1) (37 degrees C).     

Enhanced endothelin(A) receptor-mediated calcium mobilization and contraction in organ cultured porcine coronary arteries

Arterial injury models for coronary artery disease have demonstrated an enhanced expression and function of either the endothelin(A) or endothelin(B) (ET(A) or ET(B)) receptor subtype. We hypothesized that organ culture would enhance the physiological function of ET receptors in the porcine right coronary artery. Arteries were either cold stored (4 degrees C) or organ cultured (37 degrees C) for 4 days. After 4 days, the artery was either 1) sectioned into rings to measure the ET-1-induced isometric tension response (3 x 10(-10)-3 x 10(-7) M), or 2) enzymatically dispersed and the isolated smooth muscle cells imaged using fura-2 to measure the myoplasmic calcium (Ca(m)) response to 3 x 10(-8) M ET-1 ( approximately EC(50)). Isometric tension and Ca(m) to ET-1 were measured in the absence and presence of bosentan (nonselective ET(A) or ET(B) receptor antagonist), BQ788 (ET(B)-selective antagonist), and BQ123 (ET(A)-selective antagonist). Compared with cold storage, organ culture induced a 2-fold increase in tension development (3 x 10(-7) M ET-1) and Ca(m) (3 x 10(-8) M ET-1), which was inhibited with bosentan, thus confirming the enhanced responses to ET-1 were due to ET receptor activation. BQ123 also inhibited the enhanced contraction and Ca(m) responses to ET-1. In contrast, BQ788 failed to inhibit tension development and Ca(m) responses to ET-1 in organ culture and cold storage. Sarafotoxin 6C (ET(B) agonist) failed to elicit an increased Ca(m) response in organ culture compared with cold storage. Our results indicate the increased tension development and Ca(m) responses to ET-1 in organ culture are attributable to ET(A) receptors, and not ET(B) receptors.     

Effect of cooling on the responses of human saphenous vein to fentanyl, remifentanil and sufentanil

We studied the vasodilatory effects of fentanyl, remifentanil and sufentanil on the human saphenous vein strips at 37, 32 and 28 degrees C. Fentanyl produced concentration-dependent relaxation of human saphenous vein strips precontracted with 5-hydroxytryptamine (5-HT) at every temperature studied. Compared with vein strips at 37 degrees C, relaxant responses to each one concentration of fentanyl were significantly reduced at 32 and 28 degrees C. Remifentanil relaxed vein strips in a concentration-dependent way and the relaxation for all concentrations were significantly greater at 32 and 28 degrees C compared with 37 degrees C. Sufentanil produced concentration-dependent relaxation in saphenous vein strips precontracted with 5-HT. These relaxant responses were similar at 32 degrees C compared with 37 degrees C. When bath temperature was lowered from 37 to 28 degrees C, the relaxant responses to sufentanil were significantly reduced. In summary, the present study suggests that cooling reduces the relaxation caused by fentanyl and sufentanil on human saphenous veins but augments the relaxation with remifentanil. The augmented vasodilatory effect of remifentanil with cooling may be useful on systemic vascular resistance and organ preservation under hypothermic conditions like cardiopulmonary bypass surgery.     

Pharmacological characterization of muscarinic receptors implicated in rabbit detrusor muscle contraction and activation of inositol phospholipid hydrolysis in rabbit detrusor and parotid gland

In the present study, we evaluated the pharmacological characteristics of the functional muscarinic receptors implicated in rabbit detrusor contraction and coupled to inositol phospholipid turnover in rabbit detrusor and parotid gland. The selectivity of several muscarinic antagonists for detrusor vs. salivary gland muscarinic receptors was also examined. The affinities for the muscarinic m1-, m2- and m3-receptor subtypes were determined using membranes from human cloned receptors expressed in CHO-K1 cells using [3H]-N-methyl scopolamine as a radioligand. Anti-muscarinic activity was determined in isolated rabbit detrusor by measuring the displacement of the contractile response to carbachol, and in rabbit detrusor and rabbit parotid by measuring the displacement of inositol phospholipid hydrolysis (total inositol phosphate accumulation) to carbachol. A significant correlation was found between the potencies to antagonize carbachol-induced rabbit detrusor contraction (pK(B)) and the affinities (pKi) for the m3-receptor subtype (r = 0.93, P = 5 x 10(-6)). Lower, but significant, correlations [0.88 (P = 6.3 x 10(-5)), 0.72 (P = 4.6 x 10(-3))] were obtained with m1- or m2-receptor subtypes, respectively. Each muscarinic antagonist tested displayed similar potency to antagonize carbachol-stimulated inositol phospholipid hydrolysis in rabbit detrusor and parotid (r = 0.96, P = 8 x 10(-3)). A significant correlation was found between the potencies to antagonize carbachol-stimulated inositol phospholipid hydrolysis (pK(B)), determined in rabbit detrusor and rabbit parotid, and the affinities (pK(i)) for the m3-receptor subtype [r = 0.96 (P = 0.01), 0.99 (P = 5 x 10(-5)), respectively] and for the m1-receptor subtype [r = 0.98 (P = 3.5 x 10(-3)), 0.94 (P = 0.02), respectively] but not for the m2-receptor subtype [r = 0.33, 0.57, ns, respectively]. In each in vitro assay, methoctramine (preferential M2 selective antagonist) and pirenzepine (preferential M1 selective antagonist) were slightly potent. We suggest that the muscarinic receptor implicated in the response to carbachol in rabbit detrusor and parotid gland corresponds to the M3-subtype. None of the muscarinic antagonists studied in rabbit tissues displayed preferential affinity for the detrusor.     

Contribution of adrenergic and "purinergic" neurotransmission to contraction in rabbit detrusor.

In the presence of propranolol, norepinephrine produced an alpha adrenoceptor mediated contraction in isolated rabbit detrusor. Phenoxybenzamine (3.3 x 10(-8) M) antagonized this response but failed to affect the contraction produced by field stimulation either in normal or in hemicholinium-3-treated tissue. Higher concentrations of phenoxybenzamine were antagonistic to carbachol. Electrically induced contractions were also unaffected by guanethidine (1 x 10(-4) M) in vitro. Reserpine pretreatment produced no change in the contractile response although the tissue was depleted of catecholamine fluorescence on histology. It is concluded that adrenergic neurotransmission does not account for noncholinergic excitatory neurotransmission in rabbit detrusor. In rabbit detrusor adenosine 5'-triphosphate (ATP) produced a transient contraction which was not antagonized by tetrodotoxin (1 x 10(-7) M), atropine (4 x 10(-7) M) or phenoxybenzamine (3.3 x 10(-7) M). Adenosine, adenine phosphate and adenosine 5'-monophosphate had little or no effect, while sodium tripolyphosphate and adenosine 5'-diphosphate produced a smaller response than ATP. Dipyridamole (1 x 10(-8)-1 x 10(-5) M) did not unmask a response to adenosine and did not potentiate the response to ATP or field stimulation. Theophylline (5 x 10(-5) M) and 2, 2'-pyridylisatogen (PIT) (1 X 10(-5) M) depressed responses to ATP without antagonizing those to carbachol. At these doses, theophylline and 2, 2'-pyridylisatogen also antagonized the electrically induced contraction. Desensitization with ATP (1.5 X 10(-3) M for 30 min) selectively depressed responses to ATP but not to carbachol, and also depressed the response to field stimulation, particularly at frequencies of 10 Hz and lower. It is at these frequences that the noncholinergic component of the contractile response is most significant. Combination of the desensitization procedure with atropine produced an additive effect, suggesting that the two mechanisms affected are independent. Combination of the desensitization procedure with hemicholinium-3 produced less than an additive effect, suggesting an interference between the two treatments. It is concluded that ATP plays a role in the noncholinergic component of excitatory neurotransmission in rabbit detrusor.     

Differential effects of in vitro and in vivo hyperthermia on the production of interleukin-10

OBJECTIVE: To determine whether hyperthermia activates an anti-inflammatory response. DESIGN: A prospective study. SETTING: Heatstroke Center, Makkah, and King Faisal Specialist Hospital, Riyadh, Saudi Arabia. PATIENTS: Twenty-five heatstroke patients pre-cooling (rectal temperature 42.4 +/- 0.8 degrees C) (group 1) and 13 normothermic heat-stressed subjects were studied (group 2). Twelve of the 25 heatstroke patients were also studied post-cooling (group 3). Mononuclear cells from six healthy blood donors resting at 24 degrees C were used for in vitro study. INTERVENTIONS: Mononuclear cells were cultured at a concentration of 1 x 10(6)/ml without and with lipopolysaccharide (LPS) added at concentration of 10, 100, and 1000 ng/ml. The cells were incubated for 24 h at 37, 39, 41, and 43 degrees C. ELISA was used to measure IL-10 in the supernatant and plasma from heatstroke and heat-stressed subjects. RESULTS: All patients in group 1, 40% of group 2, and 37% of group 3, showed elevation of IL-10 (1289 +/- 2519, 248 +/- 393, and 172 +/- 226 pg/ml, respectively) compared with normal control levels, (< 100 pg/ml) P < 0.05. IL-10 level on admission did not correlate with degree of hyperthermia. During 24 h incubation at 37 degrees C without LPS, no IL-10 was detected, whereas with 10 ng/ml LPS, monocytes released 658 +/- 291 pg IL-10/10(6) cells. At 39 degrees C and 41 degrees C IL-10 release was decreased to 225 +/- 114, and 245 +/- 90 pg/10(6) cells, respectively; and was completely inhibited at 43 degrees C (67 +/- 10 pg/10(6) cells), P < 0.0001. CONCLUSION: Heat-stress with and without hyperthermia is associated with anti-inflammatory response in vivo. However, it does not seem to be the direct effect of heat on monocytes, suggesting that other environmental or genetic factors may be involved.     

Interaction of 5-hydroxykynurenamine, L-kynurenine and kynuramine with multiple serotonin receptors in smooth muscle

The enzymatic formation of kynurenine derivatives from tryptophan and the regulation of this metabolic pathway by both tryptophan concentrations and plasma cortisol concentrations have raised the possibility that the kynurenine derivatives, L-kynurenine, kynuramine and 5-hydroxykynurenamine (5-OH-kynurenamine) may be important as endogenous agonists or antagonists at serotonin (5-HT) receptors in smooth muscle. In fact, 5-OH-kynurenamine was an agonist at 5-HT2 receptors in the rat jugular vein and aorta, at 5-HT3 (neuronal "M") receptors in the guinea pig ileum and at 5-HT receptors in the rat stomach fundus. Maximal contractile responses to 5-OH-kynurenamine in these three smooth muscle preparations were similar to those produced by 5-HT, although 5-OH-kynurenamine was approximately 10- to 100-fold less potent than 5-HT as a contractile agonist. Using appropriate antagonists, LY53857 as a selective antagonist at 5-HT2 receptors, ICS 205-930 as a selective antagonist at 5-HT3 receptors and 1-(1-napthyl) piperazine as a potent antagonist in the rat stomach fundus, we documented further that the contractile responses to 5-OH-kynurenamine resulted from its interaction with 5-HT receptors in these tissues. Kynuramine did not contract either the rat jugular vein, aorta or the guinea pig ileum, although a contractile response did occur in the rat stomach fundus (maximal response approximately 70% of the maximal contractile response to 5-HT). High concentrations of kynuramine (10(-4) M) produced modest inhibition and reduction in maximal responses to 5-HT in the jugular vein, aorta and guinea pig ileum.(ABSTRACT TRUNCATED AT 250 WORDS)     

Protein kinase C and tracheal contraction at low temperature

During exercise or dry air-induced asthma, airway walls cool. However, the role of temperature in the regulation of airway tone is not clear. Protein kinase C (PKC) is an important second messenger in the mediation of cell responses. To explore whether changes in temperature affect pathways involving PKC in airways, we examined the effects of phorbol esters, potent activators of PKC, in guinea pig tracheal rings at various temperatures. Phorbol-12,13-diacetate (PDA) caused a reduction in tracheal tone at 37 degrees C and an increase in tone when temperature was reduced to 22 degrees C. Increases in tone were also produced by PDA when cell membranes were depolarized by ouabain (10 microM) or KCl (30 mM) at 37 degrees C. Contractions produced by PDA at 22 degrees C were inhibited by lipoxygenase inhibitors [ETYA (5,8,11,14-eicosatetraynoic acid), NDGA (nordihydroguaiaretic acid) and phenidone] and a leukotriene receptor antagonist [FPL 55712 (sodium 7-[3-(4-acetyl-3-hydroxy-2-propylphenoxy)-2-hydroxypropoxyl] -4-oxo-8-propyl-4H-1-benzopyran-2-carboxylate)]. Contractions produced by PDA at 37 degrees C or 22 degrees C in the presence of ouabain (10 mM) or KCl (30 mM) were not affected by these drugs. These results indicate that changes in temperature have profound effects on responses resulting from PKC activation. At low temperature, the lipoxygenase pathway mediates responses. Thus, cooling has the potential to modify a major intracellular pathway regulating physiological responses of the airways.     

Dissociation of myosin phosphorylation and active tension during muscarinic stimulation of tracheal smooth muscle

The Ca dependence of contraction and myosin phosphorylation was investigated in canine tracheal smooth muscle stimulated with carbachol, K or serotonin. Previous studies of tracheal muscle showed carbachol concentration-response curves for contraction and myosin phosphorylation were superposable. In contrast, there was a striking difference in the Ca++ sensitivities of tension and myosin phosphorylation when Ca++ concentration-response curves were constructed in the presence of 10(-7) M carbachol. Significant phosphorylation (greater than 0.3 moles phosphate/mole 20,000 dalton myosin light chain) was observed in the absence of active tension. In the present study, carbachol (10(-7) and 10(-6) M) and serotonin (10(-5) M) also induced significant myosin phosphorylation in low Ca++ solutions (0-0.025 mM CaCl2) without proportional increases in tension. K+ depolarization in Ca++-free physiological salt solution (60 mM KCl, 10(-6) M atropine) yielded phosphorylation not significantly different from basal levels. All stimulants induced active stress after readmission of Ca. The Ca++ dependence curve for myosin phosphorylation in muscles stimulated with carbachol was shifted up and to the left of the force curve. Atropine (10(-6) M) significantly reduced phosphorylation induced by carbachol in Ca++-free solutions, as did 3 X 10(-6) M nifedipine and 10 mM ethylene glycol bis(beta-aminoethyl ether)-N,N'-tetraacetic acid. Phorbol 12-myristate, 13-acetate or phorbol 12,13-dibutyrate did not increase basal phosphorylation or phosphorylation in low Ca++ solutions, suggesting that protein kinase C did not phosphorylate myosin in this case. Myosin phosphorylation under these conditions is not sufficient to support contraction, and is reduced by treatments that decrease Ca++ entry.(ABSTRACT TRUNCATED AT 250 WORDS)     

Pharmacological characterization of a neuronal receptor for 5-hydroxytryptamine in guinea pig ileum with properties similar to the 5-hydroxytryptamine receptor

Experiments were undertaken to characterize pharmacologically a neuronal receptor to 5-HT in guinea pig ileum. Segments of longitudinal muscle myenteric plexus preparations were treated with phenoxybenzamine and exposed to submaximal electrical field stimulation to evoke the cholinergically mediated "twitch" response. The ability of 5-HT to enhance the submaximal twitch response was investigated. Results using several antagonists (metergoline, spiperone, cyanopindolol, N-acetyl-5-hydroxytryptophyl-5-hydroxytryptophan amide, N-hexanoyl-5-hydroxytryptophyl-5-hydroxytryptophan amide, ICS 205-930, GR 38032F, MDL 72222 and cocaine) indicate that 5-HT (3 X 10(-10) to 1 x 10(-7) M) agonizes a novel 5-HT receptor site distinct from the 5-HT1, 5-HT2, 5-HT3 and 5-HT1P subtypes as well as the M receptor. The receptor site is located neuronally and is characterized positively by a low affinity for ICS 205-930 (pA2 = 6.5 vs. 5-HT) and by the following order of agonist potency: 5-HT greater than 5-methoxytryptamine greater than BRL 24924 greater than alpha-methyl-5-hydroxytryptamine greater than zacopride = cisapride = 5-carboxamidotryptamine. Agonist-independent pA2 estimates for ICS 205-930 (6.3-6.6) suggest a single site of agonism. 2-Methyl-5-hydroxytryptamine and 5-hydroxyindalpine were inactive at 1 x 10(-5) M either as agonists or antagonists. Thus, the receptor site exhibits a pharmacological profile similar to that characterizing the recently described 5-HT4 [corrected] receptor. Unlike Gaddum's M receptor, which equates with the 5-HT3 [corrected] receptor, the putative 5-HT4 [corrected] receptor site exhibits a higher sensitivity to agonism by 5-HT and is resistant to antagonism by cocaine.     

Effect of hypercarbia and shock on transcutaneous carbon dioxide at different electrode temperatures

Transcutaneous CO2 tension (PtcCO2) was measured with heated and nonheated transcutaneous carbon dioxide electrode sensors during hypercarbia and standardized hypovolemic shock in anesthetized dogs. The 95% response times of the PtcCO2 electrode, measured during step increases in FICO2 at four electrode temperatures: 37, 39, 41, and 44 degrees C, were 15, 7.5, 5, and 3.5 min, respectively. During experiments with normal cardiac output, the PtcCO2 correlated well with PaCO2 (r = 0.96). Three PtcCO2 electrode temperatures were tested for response to hypovolemic shock. Data from all PtcCO2 electrodes failed to correlate with PaCO2 during shock. PtcCO2 values rose as cardiac output decreased; there was a good negative correlation (r = -0.95). The 37 and 42 degrees C electrodes were affected by shock at cardiac index values below 2 L/min.M2; but the 44 degrees C probe was not affected until a cardiac index of 1.5 L/min.M2 was reached. Values from the 44 degrees C electrode rapidly returned to preshock values after fluid resuscitation. The response to resuscitation lagged in the 37 and 42 degrees C electrodes and did not return the preshock values until the cardiac index had been normalized for more than 15 min. It was concluded that a PtcCO2 electrode heated to 44 degrees C would be more useful in adult patients because of its faster response to hypercarbia, shock, and resuscitaton. The PtcCO2 values are higher than the corresponding PaCO2 values but they correlate well until the cardiac index (CI) falls below 1.5 L/min.M2; then PtcCO2 values have a strong negative correlation with the corresponding CI values.     

Vascular responsiveness of isolated, perfused basilar arteries in dogs and monkeys

A new model of isolated basilar arterial preparation was developed in the dog and monkey. Isolated arteries were perfused at a constant flow rate with Krebs solution and suspended in a bath at 37 degrees C. By inserting the steel cannula into the artery, the space between the luminal wall of the artery and the cannula was narrowed enough to obtain a suitable perfusion pressure during the perfusion. The resting perfusion pressure was maintained at a constant level of 50-100 mmHg. The drug solution was intraluminally administered, and the response was obtained as changes in the perfusion pressure. Responses to 6 vasoactive substances (norepinephrine, 5-HT, PGF2 alpha, histamine, ATP and KCl) were compared between simian and canine basilar arteries. It was demonstrated that in simian arteries, PGF2 alpha was the strongest but 5-HT and norepinephrine induced slight vasoconstriction to the same degree, and in canine basilar arteries, 5-HT induced the strongest constriction but norepinephrine did not produce significant vasoconstriction, and KCl induced marked constriction to the same degree at extremely large doses in both species. It was demonstrated that the cannula inserting method is useful to observe the responses of isolated basilar arteries.     

Mechanisms of extraneuronal serotonin uptake in the rat aorta

The mechanisms of extraneuronal serotonin (5-HT) uptake in the rat aorta were studied. Aortic strips were pretreated with 0.1 mM pargyline and incubated with 0.1 to 9.1 microM 5-HT (5-HT, 0.02-1.60 microgram/ml including [3H]-5-HT, 0.02 microgram/ml) for 1, 2, 3 and 5 min at 37 degrees C. Accumulation of [3H]sorbitol was used to correct for extracellular distribution of this amine. The initial rate of 5-HT uptake was related linearly to the substrate concentration within the tested range. Cocaine, imipramine, desipramine (10 microM each), Na+-free solution and cooling (0 degrees C) inhibited markedly both the 1- and 5-min uptake of 5-HT. Removal of the endothelium did not affect the 5-HT uptake for 1 min but reduced slightly that for 5 min. Corticosterone (10 microM), norepinephrine (10 microM) and 6-hydroxydopamine pretreatment did not affect the uptake of 5-HT. Autoradiography demonstrated that uptake of 5-HT for 5 min in the rat aorta occurs primarily at the smooth muscle cells near the lumen. These results suggest that the rat aorta has a large capacity of cocaine-sensitive extraneuronal uptake of 5-HT. This uptake appears to occur primarily in the muscle layers adjacent to the lumen, suggesting that the muscle cells of the luminal side function differently from those from the adventitial side. The mechanism of the extraneuronal uptake of 5-HT appears to be different from that of norepinephrine and the extraneuronal uptake of 5-HT occurs initially in a nonsaturable mode and later through a Na-dependent, carrier-mediated transport.     

Influence of lower limb pneumatic compression on pulmonary artery temperature: effect on cardiac output measurements.

OBJECTIVES: To characterize the decreases in pulmonary artery temperature that coincide with the inflation cycle of pneumatic calf compression stockings and to examine their effects on the thermodilution measurement of cardiac output. DESIGN: Three-part observational study. SETTING: University hospital surgical intensive care unit. PATIENTS: Postoperative patients with indwelling pulmonary artery catheters. INTERVENTION: Thermodilution cardiac output measurements with and without pneumatic calf compression. MEASUREMENTS AND MAIN RESULTS: Phase 1 (n = 18) examined the effects of pneumatic compression on pulmonary artery temperature. There was no effect on pulmonary artery temperature (device off, 37.468+/-0.008 degrees C; device on, 37.458+/-0.014 degrees C), but the difference between the maximum and minimum pulmonary artery temperatures was increased (off, 0.031+/-0.006 degrees C; on, 0.055+/-0.012 degrees C [p < .001]). Phase 2 (n = 12) found that the mean thermodilution cardiac output with 10 mL of cold (0-5 degrees C) injectate was unchanged by pneumatic compression (off, 7.00+/-2.28 L/min; on, 6.89+/-2.22 L/min). However, when the compression devices were operating, the variability between the individual measurements was increased, as reflected by larger coefficients of variation (off, 3.19+/-1.96; on, 8.72+/-6.56 [p < .02]). Similar results were obtained during phase 3 (n = 5), when cardiac output was measured with room temperature Injectate. CONCLUSIONS: Intermittent pneumatic calf compression increased lower limb venous return, causing acute but transient decreases in pulmonary artery blood temperature. This did not affect the accuracy of thermodilution cardiac output measurements that were made using 10 mL of either cold or room temperature injectate.     

Purinergic vasoconstrictor component revealed by moderate cooling in the isolated mesenteric vasculature of Sprague-Dawley rats.

In the isolated mesenteric vasculature of rats, moderate cooling significantly augments the perfusion pressure responses to transmural field stimulation (TFS), whereas it depresses markedly TFS-induced endogenous norepinephrine (NE) release. Moderate cooling also reduces the perfusion pressure responses to exogenous NE. The present experiments, therefore, were performed to analyze further the mechanism of the augmented pressor responses to TFS during moderate cooling. NE release from the entire mesenteric vasculature was monitored along with the perfusion pressure response to periarterial nerve stimulation (4-14 Hz) at 37 or 24 degrees C. Prazosin (3 x 10(-8) M) abolished the pressor responses to TFS at 37 degrees C but not at 24 degrees C. Furthermore, prazosin abolished the pressor responses to exogenous NE at both temperatures. The TFS-induced pressor responses observed in the presence of prazosin at 24 degrees C were abolished by alpha, beta-methylene adenosine 5'-triphosphate (alpha, beta-Me ATP) (3 x 10(-6) M). alpha, beta-Me ATP significantly decreased the pressor responses to TFS at 24 degrees C but not 37 degrees C. Moderate cooling significantly augmented the vasoconstrictor response to alpha, beta-Me ATP per se. These drugs did not influence the TFS-induced endogenous NE release at either temperature. These results suggest that moderate cooling reveals that ATP or related purines released from sympathetic nerves act as cotransmitters in the isolated mesenteric vasculature of rats. That is, augmented pressor responses to TFS during moderate cooling appeared to be due, at least in part, to a purinergic component.     

Comparative nuclear magnetic resonance studies of water permeability of red blood cells from maternal venous blood and newborn umbilical cord blood.

Comparative morphological and nuclear magnetic resonance (NMR) measurements of the diffusional permeability (Pd) were performed on red blood cells (RBCs) from maternal venous blood and fetal RBCs, isolated from cord blood taken at delivery. Fetal RBC had a diameter of 8.79+/-0.03 microm (mean+/-standard deviation, SD), a volume of 103 microm3 and a surface area of 157 microm2. We report here the first comparative measurements of Pd of maternal and fetal RBCs by using a Mn2+-doping NMR technique. The values of Pd were, in the case of maternal RBC, 3.7 x 10(-3) cm/s at 15 degrees C, 4.1 x 10(-3) cm/s at 10 degrees C, 4.9 x 10(-3) cm/s at 25 degrees C, 5.2 x 10(-3) cm/s at 30 degrees C and 7.2 x 10(-3) cm/s at 37 degrees C. For fetal RBC all corresponding Pd values were almost half, namely 2.0 x 10(-3) cm/s at 15 degrees C, 2.3 x 10(-3) cm/s at 20 degrees C, 2.8 x 10(-3) cm/s at 25 degrees C, 3.4 x 10(-3) cm/s at 30 degrees C and 4.4 x 10(-3) cm/s at 37 degrees C. The decreased Pd values of fetal RBCs were probably due to lower channel-mediated water permeability compared with adult RBCs. The values of the activation energy for water permeability (E(a,d)) were significantly higher for fetal RBCs (27.6+/-5.0 kJ/mol) than for adult RBCs (22.8+/-2.7 kJ/mol). A positive correlation between the Pd values of the two kinds of RBCs was found. This points to the genetic basis for the determination of RBC water permeability.