Developmental changes in intracellular pH buffering power in smooth muscle

Bullock, Anthony J.; Duquette, Robert A.; Buttell, N.; Wray, Susan

doi:10.1007/s004240050555

Cited by 21 publications

(23 citation statements)

References 8 publications

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“…No significant differences were found among β i values estimated for the pH i intervals ranging from 6.8 to 7.4, although a clear shift was observed for extreme pH such as 6.4. Furthermore, β i values calculated for the interval 6.8-7.4 are close to those obtained by several authors studying other cellular systems [10,13]. The average β i of these intervals was 36 mM/pH unit.…”

Section: Intracellular Buffering Powersupporting

confidence: 59%

Evidence for an electrogenic, negatively protein-kinase-A-modulated, Na + -dependent HCO 3 - transporter in human lymphocytes

Rosa¹,

Cabado

Botana

et al. 1999

Pfl�gers Archiv European Journal of Physiology

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We studied the effects of external HCO3- on pHi regulation in human lymphocytes after an acid load. Cells were acidified by preincubation with NH4Cl and pHi recovery was measured with the fluorescent dye BCECF. Cells recovering in HCO3--containing medium reached a higher final pHi, the H+ efflux rate was increased and shifted to alkaline pHi compared to that of cells recovering in HCO3--free solution. The resting pHi was higher in a HCO3--containing solution. Experiments carried out in the presence of amiloride, DIDS and in the absence of external Na+ suggest the existence of two major mechanisms acting in the pHi recovery of lymphocytes after an acid load: an amiloride-sensitive Na+/H+ exchanger and a DIDS-sensitive Na+-dependent HCO3- transporter. The last mechanism could be a Na+/HCO3- cotransporter based on membrane potential changes determined with the potential-sensitive fluorescent probe bis-oxonol. Preincubation of cells with forskolin and H-89 showed protein-kinase-A-dependent downregulation of the amiloride-insensitive recovery of pHi in human lymphocytes. In summary, this paper provides functional evidence for the existence of a Na+/HCO3--dependent mechanism involved in pHi recovery in human lymphocytes following an acid load, that is electrogenic and downregulated by PKA.

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Section: Intracellular Buffering Powersupporting

confidence: 59%

Evidence for an electrogenic, negatively protein-kinase-A-modulated, Na + -dependent HCO 3 - transporter in human lymphocytes

Rosa¹,

Cabado

Botana

et al. 1999

Pfl�gers Archiv European Journal of Physiology

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“…The tissues' buffering capacity will determine the extent of the pH i change for any given acid load. These values vary markedly between smooth muscles and little data exist for gastric smooth muscle [2,5,7]. Thus it is not known how well, or not, an acid load can be buffered by gastric myocytes.…”

Section: Introductionmentioning

confidence: 95%

pH regulation and buffering power in gastric smooth muscle

Duquette

Wray

2001

Pflügers Arch - Eur J Physiol

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Intracellular pH can have profound effects on tissue function, but little is known about how pH is regulated, buffered or affects the function of gastric smooth muscle. As the pH of gastric myocytes may alter with pathophysiological disturbance of the gastric lining, or reduction in blood flow to the stomach, these parameters were investigated. Intracellular pH was measured in strips of corpus from rats and guinea-pigs and pH perturbed by the addition of Na butyrate. pH regulation was investigated using pharmacological inhibitors and ionic substitutions. Resting pH was found to be around 7.0, and buffering power relatively high, compared to other muscles in both species. In the guinea-pig amiloride, EIPA and HOE694 prevented pH regulation from an acid load, but amiloride- and EIPA-insensitive pH-regulating mechanisms were found in the rat. The pH-regulatory mechanism present in the rat was also insensitive to DIDS, SITS and removal of external Cl-, but inhibited by Na+ substitution and HOE694. Acidification reduced gastric tone in both species. We conclude that pH alteration will significantly affect gastric contractility, despite a high capacity of the tissue to buffer and regulate pH change. The sensitivity to NHE inhibitors differs between rat and guinea-pig, suggesting that Na+/H+ exchanger isoform expression differs between gastric tissue.

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“…It may at first appear that whatever mechanism is responsible for maintaining force production in the neonatal guinea-pig, it is not associated with additional lactate production and therefore may not be glycolysis. However, we have found that pH buffering power is considerably higher in neonate tissue compared to its adult counterpart [3], reducing the fall in pH i . Therefore, the similar pH fall during metabolic inhibition does not mean that glycolysis is occurring at the same rate.…”

Section: Discussionmentioning

confidence: 97%

“…The pH i recovered back to resting levels after removal of cyanide. The mean resting levels of pH i were not significantly different between any group of animals; see also [3].…”

Section: Depolarized Preparationsmentioning

confidence: 91%

“…Intact sections of ureter (approximately 5 mm) were dissected from the central portion after removal of any fat. For measurement of intracellular pH (pH i ) the sections were incubated with the acetoxymethyl ester membrane-permeant form of carboxy-SNARF (5 µM) and for Ca 2+ measurements, Indo-1-AM (20 µM) overnight at 4°C [3,4]. After loading, the tissue was washed and placed in a small bath, approximately 200 µl, on the stage of an inverted epifluorescence microscope.…”

Section: Methodsmentioning

confidence: 99%

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Developmental and species differences in the response of the ureter to metabolic inhibition

Bullock

Wray

1998

Pfl�gers Archiv European Journal of Physiology

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The effect of inhibiting oxidative phosphorylation on electrically stimulated phasic and high-K+ depolarization-induced tonic contractions in ureteric smooth muscle has been investigated. Intracellular [Ca2+] and pH were monitored fluorimetrically with simultaneous tension measurement, in adult and neonatal rat and guinea-pig ureter. Little difference was found in the response of adult or neonatal rat ureters; cyanide abolished phasic contractions and intracellular Ca2+ transients. The contractions of the adult guinea-pig ureter were also reduced by cyanide, but not as much as those of the adult rat. Neonatal guinea-pig was, however, remarkably resistant to the effects of cyanide, with force and Ca2+ transients remaining at control levels after an initial transient dip. These differences between tissues were not apparent when a high K+ concentration was used to depolarize tissues and produce maintained [Ca2+]i and force changes; cyanide reduced force but not [Ca2+]i in all preparations. Intracellular pH decreased in all preparations with inhibition of oxidative phosphorylation, but this did not correlate with changes in contraction. It is concluded that there are both species and developmental differences in the response to metabolic inhibition of the ureter which lead to differing changes in contractile activity.

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Developmental changes in intracellular pH buffering power in smooth muscle

Cited by 21 publications

References 8 publications

Evidence for an electrogenic, negatively protein-kinase-A-modulated, Na + -dependent HCO 3 - transporter in human lymphocytes

Evidence for an electrogenic, negatively protein-kinase-A-modulated, Na + -dependent HCO 3 - transporter in human lymphocytes

pH regulation and buffering power in gastric smooth muscle

Developmental and species differences in the response of the ureter to metabolic inhibition

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