共查询到20条相似文献,搜索用时 31 毫秒
1.
《Respiration physiology》1990,79(3):219-229
CO2 binding in whole blood and true plasma of the eel was estimated by measuring CO2 content and pH in blood aliquots equilibrated with various PCO2 values over a wide range expected to occur in the swimbladder. Bicarbonate concentration, [HCO3−], was calculated using the CO2 solubility coefficient, which was measured to average 50 μmol·L−1·Torr−1 (20°C). Buffer lines of non-bicarbonate buffers were obtained in plots of [HCPO3−] against pH, and non-bicarbonate buffer values, βNB, were obtained by curve. fitting.In the pH range 6.6–8.2, the buffer line for oxygenated whole blood was sigmoid, while that for deoxygenated blood increased its slope monotonously with increasing pH. The βNB for oxygenated blood displayed a maximum of about 8.6 mmol·L−1pH−1 at pH = 7.4 and dropped down to below 1 mmol·L−1·pH−1 at higher and lower pH. Similar shapes of the buffer lines were obtaned in true plasma; the [HCO3−] levels and βNB values were, however, somewhat higher than in whole blood.These data are useful fo assess the back-diffusion of CO2 and HCO3− in the rete mirabile of the fish swimbladder and to estimate the effects CO2 back-diffusion exerts on the counter-current enhancement of O2 in the rete. 相似文献
2.
Meike Stumpp Marian Y. Hu Frank Melzner Magdalena A. Gutowska Narimane Dorey Nina Himmerkus Wiebke C. Holtmann Sam T. Dupont Michael C. Thorndyke Markus Bleich 《Proceedings of the National Academy of Sciences of the United States of America》2012,109(44):18192-18197
Calcifying echinoid larvae respond to changes in seawater carbonate chemistry with reduced growth and developmental delay. To date, no information exists on how ocean acidification acts on pH homeostasis in echinoderm larvae. Understanding acid–base regulatory capacities is important because intracellular formation and maintenance of the calcium carbonate skeleton is dependent on pH homeostasis. Using H+-selective microelectrodes and the pH-sensitive fluorescent dye BCECF, we conducted in vivo measurements of extracellular and intracellular pH (pHe and pHi) in echinoderm larvae. We exposed pluteus larvae to a range of seawater CO2 conditions and demonstrated that the extracellular compartment surrounding the calcifying primary mesenchyme cells (PMCs) conforms to the surrounding seawater with respect to pH during exposure to elevated seawater pCO2. Using FITC dextran conjugates, we demonstrate that sea urchin larvae have a leaky integument. PMCs and spicules are therefore directly exposed to strong changes in pHe whenever seawater pH changes. However, measurements of pHi demonstrated that PMCs are able to fully compensate an induced intracellular acidosis. This was highly dependent on Na+ and HCO3−, suggesting a bicarbonate buffer mechanism involving secondary active Na+-dependent membrane transport proteins. We suggest that, under ocean acidification, maintained pHi enables calcification to proceed despite decreased pHe. However, this probably causes enhanced costs. Increased costs for calcification or cellular homeostasis can be one of the main factors leading to modifications in energy partitioning, which then impacts growth and, ultimately, results in increased mortality of echinoid larvae during the pelagic life stage. 相似文献
3.
Jean-Claude Henquin 《Molecular and cellular endocrinology》1981,21(2):119-128
The influence of pH on the K+ permeability of pancreatic islet cells was investigated by measuring 86Rb+ fluxes in isolated rat islets perifused or incubated in the absence of glucose. Acidification of the medium (to pH 6.5), by decreasing the concentration of HCO?3 or by increasing pCO2 at constant HCO?3 reversibly reduced the rate of 86Rb+ efflux from perifused islets. Alkalinization of the medium (to pH 7.8), by decreasing the pCO2, reversibly increased 86Rb+ efflux. Similar changes were recorded upon alteration of the pH in a bicarbonate-free, Hepesbuffered medium with or without calcium. Alteration of the CO2 level at constant external pH — in order to modify internal pH — produced only a small and transient increase in efflux rate when CO2 was lowered, and a decrease in efflux rate when CO2 was raised. NH4Cl reversibly augmented 86Rb+ efflux in the presence and in the absence of HCO?3. At low pH (6.5), 86Rb+ uptake by islet cells was reduced after 10 min (25%) and 30 min (11%), but not after 60 min, of incubation; it was not significantly affected by high pH (7.8). Calcium uptake and insulin release were reduced at low pH and increased at high pH.These results show that the K+ permeability of islet cells is affected by changes in extracellular but not in intracellular pH. They suggest that the endogenous production of protons that accompanies glucose stimulation of islet cells is not the mediator of the decrease in K+ permeability induced by the sugar. 相似文献
4.
Richard D. Vaughan-Jones Kenneth W. Spitzer 《Journal of molecular and cellular cardiology》2009,46(3):318-331
Intracellular pH (pHi) is an important modulator of cardiac excitation and contraction, and a potent trigger of electrical arrhythmia. This review outlines the intracellular and membrane mechanisms that control pHi in the cardiac myocyte. We consider the kinetic regulation of sarcolemmal H+, OH− and HCO3− transporters by pH, and by receptor-coupled intracellular signalling systems. We also consider how activity of these pHi effector proteins is coordinated spatially in the myocardium by intracellular mobile buffer shuttles, gap junctional channels and carbonic anhydrase enzymes. Finally, we review the impact of pHi regulatory proteins on intracellular Ca2+ signalling, and their participation in clinical disorders such as myocardial ischaemia, maladaptive hypertrophy and heart failure. Such multiple effects emphasise the fundamental role that pHi regulation plays in the heart. 相似文献
5.
Markus Sj?blom Anurag Kumar Singh Wen Zheng Jian Wang Bi-guang Tuo Anja Krabbenh?ft Brigitte Riederer Gerolf Gros Ursula Seidler 《Proceedings of the National Academy of Sciences of the United States of America》2009,106(31):13094-13099
Carbonic anhydrase (CA) is strongly expressed in the duodenum and has been implicated in a variety of physiological functions including enterocyte HCO3− supply for secretion and the “sensing” of luminal acid and CO2. Here, we report the physiological role of the intracellular CAII isoform involvement in acid-, PGE2, and forskolin-induced murine duodenal bicarbonate secretion (DBS) in vivo. CAII-deficient and WT littermates were studied in vivo during isoflurane anesthesia. An approximate 10-mm segment of the proximal duodenum with intact blood supply was perfused under different experimental conditions and DBS was titrated by pH immediately. Two-photon confocal microscopy using the pH-sensitive dye SNARF-1F was used to assess duodenocyte pHi in vivo. After correction of systemic acidosis by infusion of isotonic Na2CO3, basal DBS was not significantly different in CAII-deficient mice and WT littermates. The duodenal bicarbonate secretory response to acid was almost abolished in CAII-deficient mice, but normal to forskolin- or 16,16-dimethyl PGE2 stimulation. The complete inhibition of tissue CAs by luminal methazolamide and i.v. acetazolamide completely blocked the response to acid, but did not significantly alter the response to forskolin. While duodenocytes acidified upon luminal perfusion with acid, no significant pHi change occurred in CAII-deficient duodenum in vivo. The results suggest that CA II is important for duodenocyte acidification by low luminal pH and for eliciting the acid-mediated HCO3− secretory response, but is not important in the generation of the secreted HCO3− ions. 相似文献
6.
The effect of 4,4′-diisothiocyanato-stilbene-2,2′-disulfonate on CO2 permeability of the red blood cell membrane
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R. E. Forster G. Gros L. Lin Y. Ono M. Wunder 《Proceedings of the National Academy of Sciences of the United States of America》1998,95(26):15815-15820
It has long been assumed that the red cell membrane is highly permeable to gases because the molecules of gases are small, uncharged, and soluble in lipids, such as those of a bilayer. The disappearance of 12C18O16O from a red cell suspension as the 18O exchanges between labeled CO2 + HCO3− and unlabeled HOH provides a measure of the carbonic anhydrase (CA) activity (acceleration, or A) inside the cell and of the membrane self-exchange permeability to HCO3− (Pm,HCO−3). To test this technique, we added sufficient 4,4′-diisothiocyanato-stilbene-2,2′-disulfonate (DIDS) to inhibit all the HCO3−/Cl− transport protein (Band III or capnophorin) in a red cell suspension. We found that DIDS reduced Pm,HCO−3 as expected, but also appeared to reduce intracellular A, although separate experiments showed it has no effect on CA activity in homogenous solution. A decrease in Pm,CO2 would explain this finding. With a more advanced computational model, which solves for CA activity and membrane permeabilities to both CO2 and HCO3−, we found that DIDS inhibited both Pm,HCO−3 and Pm,CO2, whereas intracellular CA activity remained unchanged. The mechanism by which DIDS reduces CO2 permeability may not be through an action on the lipid bilayer itself, but rather on a membrane transport protein, implying that this is a normal route for at least part of red cell CO2 exchange. 相似文献
7.
《Respiration physiology》1994,95(2):209-226
We studied the effect of hypercapnic and fixed acid central chemoreceptor stimulation on the pneumostone in the pulmonate snail, Helix aspersa. We found that focal stimulation of the central chemoreceptor area of the pulmonate snail brain with hypercapnic solutions more effectively increased the pneumostonal area than did fixed acid stimulation at the same extracellular pH. Disrupting intracellular pH regulation by inhibiting Cl− transport, either pharmacologically (DIDS) or by ion substitution (Cl−-free perfusate), enhanced pneumostomal responses to CO2. While maintaining a constant perfusate pH, addition of NH4Cl to the perfusate resulted in pneumostomal closure; whereas removal of NH4Cl from the bath resulted in pneumostomal opening. In conclusion, the ventilatory response to CO2 in H. aspersa does not require Cl− transport or conductance. Furthermore, changing pHi alone is an adequate stimulus for the central chemoreceptors in the snail. 相似文献
8.
Summary This study investigated the effect of acidosis on intracellular pH (pHi), intracellular calcium concentration ([Ca]i), and vascular contraction in the aorta of the newborn and adult rabbit. Isometric tension, pHi, and [Ca]i were measured in an isolated ring preparation. After the vascular contraction was induced with 50 mM KCl, the effect of respiratory
acidosis produced by elevation of PCO2 was studied. Respiratory acidosis caused a transient depression followed by a recovery of contractile tension. The decrease
in developed tension was greater in the newborn than in the adult. The decrease in pHi during acidosis was similar in the two age groups. [Ca]i increased during acidosis and the increase was greater in the newborn than in the adult. These data show that the vasorelaxant
effect of acidosis in the newborn aorta is greater than that in the adult aorta. The greater vasodilation in the newborn cannot
be explained by the difference in pHi or [Ca]i. 相似文献
9.
Tomohiro Yasuda Takashi Abe Haruko Iida Kentaro Meguro Satoshi Fujita 《Metabolism: clinical and experimental》2010,59(10):1510-1519
The effect of low-intensity resistance exercise with external limb compression (100 [EC100] and 160 [EC160] mm Hg) on limb blood flow and venous blood gas-metabolite response was investigated and compared with that of high-intensity resistance exercise (no external compression). Unilateral elbow flexion muscle contractions were performed at 20% (75 repetitions, 4 sets, 30-second rest intervals) and 70% of 1-repetition maximum (1-RM; 3 sets, each set was until failure, 3-minute rest intervals). Precontraction brachial arterial blood flow (Doppler ultrasound) was reduced with EC100 or EC160 (56% and 39% of baseline value, respectively) compared with no external compression (control). At 20% 1-RM, brachial arterial blood flow increased after contractions performed with EC160 (190%), but not with the others. Decreases in venous oxygen partial pressure (PvO2) and venous oxygen saturation (SvO2) were greater during EC100 and EC160 than control (mean [SE]: PvO2, 28 [3] vs 26 [2] vs 33 [2] mm Hg; SvO2, 41% [5%] vs 34% [4%] vs 52% [5%], respectively). Changes in venous pH (pHv), venous carbon dioxide partial pressure (PvCO2), and venous lactate concentration ([L−]v) were greater with EC160 than EC100 and/or control (pHv, 7.19 [0.01] vs 7.25 [0.01] vs 7.27 [0.02]; PvCO2, 72 [3] vs 64 [2] vs 60 [3] mm Hg; [L−]v, 5.4 [0.6] vs 3.7 [0.4] vs 3.0 [0.4] mmol/L, respectively). Seventy percent 1-RM contractions resulted in greater changes in pHv (7.14 [0.02]), PvCO2 (91 [5] mm Hg), and [L−]v (7.0 [0.5] mmol/L) than EC100 and EC160, but PvO2 (30 [4] mm Hg) and SvO2 (40% [3%]) were similar. In conclusion, changes in pHv, PvCO2, and [L−]v, but not in PvO2 and SvO2, are sensitive to changes in relative, “internal” intensity of low-intensity muscle contractions caused by reduced blood flow (EC160) or high-intensity muscle contractions. Given the magnitude of the changes in pHv, PvCO2, and [L−]v, it appears plausible that they may be involved in stimulating the observed increase in muscle activation via group III and IV afferents. 相似文献
10.
Ana Kili? 《Journal of molecular and cellular cardiology》2009,46(3):360-369
Estrogen has been shown to protect the heart and attenuate myocardial hypertrophy and left ventricular remodelling through as yet to be defined mechanisms. In the present study we examined concentration-dependent effects of estrogen on hypertrophy of adult rat cardiomyocytes, potential underlying mechanisms related to intracellular pH (pHi) and possible sex-dependent responses. Cardiomyocytes were isolated from adult male and female Sprague-Dawley rats and used immediately for pHi determinations or cultured and subsequently treated for 24 h with 17β-estradiol to assess hypertrophic responses. Fluorometric measurements with the pHi-sensitive dye BCECF demonstrated that at 1 pM 17β-estradiol increased pHi (+ 0.05 pH units in females and + 0.12 pH units in males, P < 0.05) by a rapid non-genomic mechanism that was blocked by the sodium-hydrogen exchange isoform 1 (NHE-1) specific inhibitor AVE-4890 (AVE, 5 μM). Treatment with 1 pM 17β-estradiol for 24 h increased cell size (females: 20%, P < 0.05; males: 29%, P < 0.05) and ANP expression (females: 414%, P < 0.05; males: 497%, P < 0.05) in a NHE-1-, and ERK1/2 MAPK-dependent manner. At 1 nM, 17β-estradiol decreased pHi (females: − 0.24 pH units, P < 0.05; males: − 0.07 pH units, P < 0.05) which was also prevented by AVE, although at this concentration the hormone had no direct hypertrophic effect but instead prevented hypertrophy induced by phenylephrine. Our results show that low levels of estrogen produce cardiomyocyte hypertrophy through ERK/NHE-1 activation and intracellular alkalinization whereas an antihypertrophic effect is seen at high concentrations. These effects may further our understanding of the role of estrogen in heart disease particularly associated with hypertrophy. 相似文献
11.
Antonio Benedetti Gianluca Svegliati Baroni Luca Marucci Raniero Mancini Cristina Bassotti Giampiero Macarri 《Alcoholism, clinical and experimental research》1995,19(1):216-225
The aim of this study was to gain information on intracellular pH (pHi) regulation in periportal (PP) and perivenular (PV) hepatocytes isolated from rats pair-fed liquid diets with either ethanol (T rats) or isocaloric carbohydrates (C rats). pHi was analyzed by the pH-sensitive dye BCECF in perfused sub-confluent hepatocyte monolayers. Cells were acid-loaded by pulse exposure to NH4Cl and were alkali-loaded by suddenly reducing external C02 and HC03-(from 10% and 50 mm , respectively, to 5% and 25 mm ) at constant pHout. In cells from C rats: (a) steady-state pHi was higher in PP than in PV hepatocytes in the presence, but not in the absence, of bicarbonate; (b) pHi recovery from an acid load was 35% higher in PP than in PV cells in the presence of HC03-, whereas it was similar in HC03--free experiments; and, on the contrary, (c) pHi recovery from an alkaline load was 30% higher in PV than in PP cells. In cells from T rats: (a) steady-state pHi was always lower than in cells isolated from pair-fed animals; (b) steady-state pHi was similar in PP and PV hepatocytes either in the presence or absence of bicarbonate in the perfusate; (c) pHi recovery from an acid load was not significantly different in PP and PV cells either in the presence of HC03- or in HC03--free experiments; and (d) pHi recovery from an alkaline load was similar in PP and PV cells. Our data suggest that chronic ethanol treatment selectively modifies pH, by affecting the activity of ion transport mechanisms regulating pHi in PP and PV hepatocytes isolated from rat liver. 相似文献
12.
Intracellular Na+ ([Na+] i ) is an important modulator of excitation–contraction coupling via regulating Ca2+ efflux/influx, and no investigation has been so far performed in diabetic rat heart. Here, we examined whether any change of [Na+] i in paced cardiomyocytes could contribute to functional alterations during diabetes. Slowing down in depolarization phase of the action potential, small but significant decrease in its amplitude with a slight depolarized resting membrane potential was traced in live cardiomyocytes from diabetic rat, being parallel with a decreased TTX-sensitive Na+ channel current (I Na) density. We recorded either [Na+] i or [Ca2+] i by using a fluorescent Na+ indicator (SBFI-AM or Na-Green) or a Ca2+ indicator (Fura 2-AM) in freshly isolated cardiomyocytes. We examined both [Na+] i and [Ca2+] i at rest, and also [Na+] i during pacing with electrical field stimulation in a range of 0.2–2.0 Hz stimulation frequency. In order to test the possible contribution of Na+/H+ exchanger (NHE) to [Na+] i , we examined the free cytoplasmic [H+] i changes from time course of [H+] i recovery in cardiomyocytes loaded with SNARF1-AM by using ammonium prepulse method. Our data showed that [Na+] i in resting cells from either diabetic or control group was not significantly different, whereas the increase in [Na+] i was significantly smaller in paced diabetic cardiomyocytes compared to that of the controls. However, resting [Ca2+] i in diabetic cardiomyocytes was significantly higher than that of the controls. Here, a lower basal pH i in diabetics compared with the controls correlates also with a slightly higher but not significantly different NHE activity and consequently a similar Na+ loading rate at resting state with a leftward shift in pH sensitivity of NHE-dependent H+-flux. NHE protein level remained unchanged, while protein levels of Na+/K+ ATPase and Na+/Ca2+ exchanger were decreased in the diabetic cardiomyocytes. Taken together, the present data indicate that depressed I Na plays an important role in altered electrical activity with less Na+ influx during contraction, and an increased [Ca2+] i load in these cells seems to be independent of [Na+] i . The data with insulin treatment suggest further a recent balance between Na+ influx and efflux proteins associated with the [Na+] i , particularly during diabetes. 相似文献
13.
The acid-base status and functional responses of alveolar macrophages (m) are influenced by the activity of plasmalemmal V-type H+-pump (V-ATPase), an electrogenic H+ extruder that provides a possible link between intracellular pH (pHi) and plasma membrane potential (Em). This study examined the relationships among Em, pHi, and plasmalemmal V-ATPase activity in resident alveolar m from rabbits. Em and pHi were measured using fluorescent probes. Em was –46 mV and pHi was 7.14 at an extracellular pH (pHo) of 7.4. The pHi declined progressively at lower pHo values. Decrements in pHo also caused depolarization of the plasma membrane, independent of V-ATPase activity. The pH effects on Em were sensitive to external K+, and hence, probably involved pH-sensitive K+ conductance. H+ were not distributed at equilibrium across the plasma membrane. V-ATPase activity was a major determinant of the transmembrane H+ disequilibrium. Pump inhibition with bafilomycin A1 caused cytosolic acidification, due most likely to the retention of metabolically generated H+. V-ATPase inhibition also caused depolarization of the plasma membrane, but the effects were mediated indirectly via the accompanying pHi changes. V-ATPase activity was sensitive to Em. Em hyperpolarization (valinomycin-clamp) reduced V-ATPase activity, causing an acidic shift in baseline pHi under steady-state conditions and slowing pHi recovery from NH4Cl prepulse acid-loads. The findings indicate that a complex relationship exists among Em, pHi, and pHo that was partially mediated by plasmalemmal V-ATPase activity. This relationship could have important consequences for the expression of pH- and/or voltage-sensitive functions in alveolar m. 相似文献
14.
In order to study the effect of prolonged elevation of plasma inorganic phosphate (P1) on red cell metabolism and function, oxyhemolobin dissociation curves (ODC) from zero to full saturation were performed on whole blood from 14 insulintreated, nonacidotic diabetics and 5 healthy volunteers following oral administration of disodium ethane-l-hydroxy-l, l-diphosphonate (EHDP; 20 mg kg?1 day?1 or placebo for 28 days. EHDP significantly increased mean Pi (diabetics, 1.18 to 1.67 mmol/liter; P < 0.001; controls 1.14 to 1.69 mmol/liter; P < 0.005 and P50 at in vivo pH of the ODC (diabetics, 25.6 to 26.7 mm Hg, P < 0.025; controls, 27.6 to 29.5 mm Hg, P < 0.02). Pi and P50 were correlated in both diabetics (r = 0.58, P < 0.01) and controls (r = 0.69, P < 0.05). Mean P50 in diabetics was significantly lower than normal in spite of normal red cell 2,3-diphosphoglycerate (2,3-DPG) (diabetics, 15.2μmol/g of Hb; controls, 14.3 μmol/g of Hb). 2,3-DPG increased when the diabetics were on EHDP (15.2 to 16.3 μmol/g of Hb, P < 0.005), while no significant changes occurred in hemoglobin concentration, oxygen saturation, or blood pH. The study emphasizes the importance of Pi on red cell function and indicates that an elevation of Pi tends to counteract the defect in oxygen-release capacity of the red cells in diabetic subjects. 相似文献
15.
Characterization of a novel cell damage model induced by acid and pepsin using rat gastric epithelial cells: Protective effect of sucralfate 总被引:1,自引:0,他引:1
We have established a new model for rat gastric epithelial cell (RGM1) damage caused by both acid and pepsin. Exposure of RGM1 to an acidified medium (pH 3.5–5.0) for 10-50 min decreased cell viability in a time- and pH-dependent manner. Pepsin (0.5–1.0 mg/mL) at pH 4.5 potentiated cell damage in a concentration-dependent manner. Based on these results, two types of cell damage models caused by incubation of cells at pH 4.0 and with pepsin (0.75 mg/mL) at pH 4.5 for 30 min, respectively, were established. The intracellular pH (pH) gradually decreased with a decrease in medium pH and an increase in exposure time. At pH ≤ 4.0, pHi reached approximately pH 6.3. Pepsin at pH 4.5 caused a further reduction in pHi compared with the acidified medium alone. Pepsin pre-incubated with pepstatin did not induce any cell damage. Pretreatment with sucralfate (0.1 -3 mg/mL) for 2 h significantly prevented cell damage caused at both pH 4.0 and with pepsin at pH 4.5 in a concentration-dependent manner. Sucralfate (3 mg/mL) significantly prevented the reduction in pHi at pH 4.0 or with pepsin at pH 4.5. 16,16-Dimethyl prostaglandin E2 (30 μg/mL) had no effect on either cell damage or pHi. These cell damage models involving RGM1 are useful for studying the mechanism underlying cell damage and for the screening of cytoprotective drugs. 相似文献
16.
Alveolar macrophages (mφ) possess two parallel mechanisms for plasmalemmal H+ extrusion: a V-type H+ pump (V-ATPase) and a Na+/H+ exchanger (NHE). To investigate the coordinated functioning of these H+ extruders for mφ intracellular pH (pHi) regulation, we investigated the effects of the plant lectin concanavalin A (ConA) on resident alveolar mφ from rabbits.
ConA (1 μM, 30-min pretreatment) activated the mφ for phagocytosis of opsonized Escherichia coli. ConA activation did not affect the baseline pHi of mφ or the initial rate of pHi recovery (dpHi/dt) from an intracellular acid load (acid-loaded pHi nadir ≈ 6.9). However, the contributions of Na+-independent H+ transport (i.e. V-ATPase activity) and Na+-dependent H+ transport (i.e. NHE activity) to dpHi/dt were altered significantly. The lectin stimulated Na+/H+ exchange and inhibited V-ATPase activity. In control mφ, V-ATPase-mediated H+ extrusion was responsible for >80% of dpHi/dt. Conversely, in ConA-treated mφ, Na+/H+ exchange was responsible for ∼65% of dpHi/dt, and V-ATPase activity was responsible for only 35% of dpHi/dt. These results underscore the complex mechanisms and signaling pathways that coordinate the activities of cellular acid-base
transporters in mφ pHi regulation.
Accepted for publication: 18 March 1997 相似文献
17.
Local anesthetics influence a variety of stimulus-induced effector functions in leukocytes. The present study determined
the effects of lidocaine on intracellular pH (pHi) regulation, superoxide production, and tumor necrosis factor-α (TNF-α) release in alveolar macrophages (mφ). Resident mφ
were obtained by bronchoalveolar lavage of rabbits. The cells were subjected to an intracellular acid load, and subsequent
pHi recovery was followed in the presence or absence of bafilomycin A1, a specific inhibitor of V-type H+-translocating ATPase (V-ATPase) or amiloride, an inhibitor of Na+/H+ exchange. Lidocaine slowed pHi recovery in a dose-dependent manner. Pretreatment (1 h) with 2.5 mM lidocaine abolished Na+/H+ exchange and reduced the V-ATPase-mediated component of pHi recovery. Lidocaine also significantly depressed the superoxide production induced by phorbol ester. TNF-α release induced
by endotoxin was not affected significantly by the local anesthetic. Macrophage viability (trypan blue exclusion) and cellular
ATP concentration were unaffected. These results indicate that lidocaine inhibits pHi regulatory mechanisms in alveolar mφ. This disruption of pHi regulation could contribute to inhibitory actions of lidocaine on mφ effector functions.
Accepted for publication: 28 January 1997 相似文献
18.
Martín Vila-Petroff Noelia Lezcano María Ana Huergo Metin Avkiran 《Journal of molecular and cellular cardiology》2010,49(1):106-939
The Na+/H+ exchanger (NHE-1) plays a key role in pHi recovery from acidosis and is regulated by pHi and the ERK1/2-dependent phosphorylation pathway. Since acidosis increases the activity of Ca2+/calmodulin-dependent protein kinase II (CaMKII) in cardiac muscle, we examined whether CaMKII activates the exchanger by using pharmacological tools and highly specific genetic approaches. Adult rat cardiomyocytes, loaded with the pHi indicator SNARF-1/AM were subjected to different protocols of intracellular acidosis. The rate of pHi recovery from the acid load (dpHi/dt)—an index of NHE-1 activity in HEPES buffer or in NaHCO3 buffer in the presence of inhibition of anion transporters—was significantly decreased by the CaMKII inhibitors KN-93 or AIP. pHi recovery from acidosis was faster in CaMKII-overexpressing myocytes than in overexpressing β-galactosidase myocytes (dpHi/dt: 0.195 ± 0.04 vs. 0.045 ± 0.010 min− 1, respectively, n = 8) and slower in myocytes from transgenic mice with chronic cardiac CaMKII inhibition (AC3-I) than in controls (AC3-C). Inhibition of CaMKII and/or ERK1/2 indicated that stimulation of NHE-1 by CaMKII was independent of and additive to the ERK1/2 cascade. In vitro studies with fusion proteins containing wild-type or mutated (Ser/Ala) versions of the C-terminal domain of NHE-1 indicate that CaMKII phosphorylates NHE-1 at residues other than the canonical phosphorylation sites for the kinase (Ser648, Ser703, and Ser796). These results provide new mechanistic insights and unequivocally demonstrate a role of the already multifunctional CaMKII on the regulation of the NHE-1 activity. They also prove clinically important in multiple disorders which, like ischemia/reperfusion injury or hypertrophy, are associated with increased NHE-1 and CaMKII. 相似文献
19.
《American journal of hypertension》2002,15(4):291-295
BackgroundIntracellular ionized calcium ([Ca2+]i) is a key mediator in the activation and oxidant production by peripheral polymorphonuclear leukocytes (PMN). Primed PMN contribute to oxidative stress (OS) and inflammation in essential hypertension (EH). Elevated [Ca2+]i has been described in insulin-resistant states and in various cell types in EH but not in EH PMN. The aim of this study was to evaluate the levels of [Ca2+]i in peripheral EH PMN in relation to plasma insulin levels and blood pressure (BP).MethodsThe PMN were separated from blood of 20 nonsmoking, nonobese untreated EH patients, age range 20 to 60 years and from 20 age- and gender-matched healthy individuals (NC). Plasma glucose and insulin levels 2 h after a 75-g oral glucose load, reflected insulin resistance. PMN [Ca2+]i was measured by flow cytometry in isolated cells stained with Fluo-3.ResultsThe EH PMNs showed significantly increased [Ca2+]i compared to NC PMN. Eighty percent of EH patients showed significantly higher plasma insulin levels after glucose load. Linear regression analysis showed significant correlation between 1) PMN [Ca2+]i and mean arterial pressure (MAP) (r = 0.5, P < .006); 2) PMN [Ca2+]i and fasting plasma insulin (r = 0.7, P < .005); and 3) fasting plasma insulin and MAP (r = 0.4, P < .04).ConclusionsThis study adds PMN to previously described cells exhibiting elevated [Ca2+]i, contributing to OS and inflammation. The correlation of individual BP with both PMN [Ca2+]i and plasma insulin levels, together with the fact that elevated [Ca2+]i mediates PMN priming, suggest that elevated [Ca2+]i and insulin are involved in the pathogenesis of hypertension-induced vascular injury in EH. 相似文献
20.
《American journal of hypertension》1998,11(1):113-116
Hyperlipidemia is an established risk factor for progressive renal damage and proteinuria. Platelets and vascular smooth muscle cells (VSMC) are known to possess low density lipoprotein (LDL) cholesterol receptors. We used platelet LDL receptors to investigate the hypothesis that elevated lipids could activate intracellular calcium [Ca2+]i signals, leading to altered vascular tone and permeability. We divided essential hypertensives into microalbuminuric positive (MA+) and negative (MA−) groups and measured baseline and LDL stimulated levels of [Ca2+]i. The MA+ group demonstrated a significantly higher mean baseline [Ca2+]i level (119.0 ± 24.5 v 86.2 ± 25.4 μmol/mL, P = .001). The MA+ group also displayed greater elevations in [Ca2+]i levels after stimulation with LDL in concentrations of 10 and 25 μg/mL (100.9 ± 54.8 v 40.9 ± 20.2, P = .04 and 111.6 ± 51.0 v 52.9 ± 39.9 μmol/mL, P = .03, respectively). Our data indicate that hypertensive patients with early glomerular capillary injury display exaggerated influx of [Ca2+]i after LDL receptor stimulation. Heightened LDL receptor sensitivity may facilitate LDL mediated [Ca2+]i signals, leading to increased VSMC tone and proliferation and progressive renal disease. 相似文献