Na+/H+ exchange and osmotic shrinkage in isolated trout hepatocytes

1997 ◽  
Vol 200 (17) ◽  
pp. 2369-2376 ◽  
Author(s):  
B Fossat ◽  
J Porthé-Nibelle ◽  
S Pedersen ◽  
B Lahlou
Keyword(s):  
Rainbow Trout ◽  
Intracellular Ph ◽  
Extracellular Ph ◽  
Hypertonic Medium ◽  
Volume Increase ◽  
Regulatory Volume Increase ◽  
Hypertonic Stress ◽  
Amiloride Derivatives ◽  
Na Uptake ◽  
Rainbow Trout Liver

The ability of rainbow trout liver cells to regulate their intracellular pH (pHi) was studied using two methods on hepatocytes isolated by collagenase digestion: (i) by monitoring pHi with the fluorescent dye BCECF-AM, and (ii) by measuring the amiloride-sensitive uptake of 22Na, which represents Na+/H+ exchange. In low-Na+ medium (¾16mmoll-1), Na+ uptake was reduced by approximately 70% in the presence of amiloride derivatives (DMA or MPA, 10(-4)moll-1). Changing separately either the extracellular pH (pHe) or the intracellular pH (pHi, clamped by treating the cells with nigericin in the presence of 140mmoll-1 K+) between 6 and 8 induced an increase in the rate of Na+ uptake when pHe was raised or when pHi was reduced. When transferred to hypertonic medium, hepatocytes shrank to nearly 72% of their initial volume, and thereafter a slow and partial regulatory volume increase phase was observed, with an increase in the amiloride-sensitive rate of Na+ uptake and an increase in intracellular pH. As DIDS-sensitive Cl- uptake was concomitantly enhanced, it is suggested that hypertonic stress activates Na+/H+ and Cl-/HCO3- exchange.

scholarly journals Hypertonic stress increases the Na+ conductance of rat hepatocytes in primary culture.

1995 ◽  
Vol 105 (4) ◽  
pp. 507-535 ◽  
Author(s):  
F Wehner ◽  
H Sauer ◽  
R K Kinne
Keyword(s):  
Cell Membrane ◽  
Primary Culture ◽  
Regulatory Volume Decrease ◽  
Rat Hepatocytes ◽  
Laser Scanning Microscopy ◽  
Specific Cell ◽  
Volume Increase ◽  
Regulatory Volume Increase ◽  
Hypertonic Stress ◽  
Cell Volumes

We studied the ionic mechanisms underlying the regulatory volume increase of rat hepatocytes in primary culture by use of confocal laser scanning microscopy, conventional and ion-sensitive microelectrodes, cable analysis, microfluorometry, and measurements of 86Rb+ uptake. Increasing osmolarity from 300 to 400 mosm/liter by addition of sucrose decreased cell volumes to 88.6% within 1 min; thereafter, cell volumes increased to 94.1% of control within 10 min, equivalent to a regulatory volume increase (RVI) by 44.5%. This RVI was paralleled by a decrease in cell input resistance and in specific cell membrane resistance to 88 and 60%, respectively. Ion substitution experiments (high K+, low Na+, low Cl-) revealed that these membrane effects are due to an increase in hepatocyte Na+ conductance. During RVI, ouabain-sensitive 86Rb+ uptake was augmented to 141% of control, and cell Na+ and cell K+ increased to 148 and 180%, respectively. The RVI, the increases in Na+ conductance and cell Na+, as well as the activation of Na+/K(+)-ATPase were completely blocked by 10(-5) mol/liter amiloride. At this concentration, amiloride had no effect on osmotically induced cell alkalinization via Na+/H+ exchange. When osmolarity was increased from 220 to 300 mosm/liter (by readdition of sucrose after a preperiod of 15 min in which the cells underwent a regulatory volume decrease, RVD) cell volumes initially decreased to 81.5%; thereafter cell volumes increased to 90.8% of control. This post-RVD-RVI of 55.0% is also mediated by an increase in Na+ conductance. We conclude that rat hepatocytes in confluent primary culture are capable of RVI as well as of post-RVD-RVI. In this system, hypertonic stress leads to a considerable increase in cell membrane Na+ conductance. In concert with conductive Na+ influx, cell K+ is then increased via activation of Na+/K(+)-ATPase. An additional role of Na+/H+ exchange in the volume regulation of rat hepatocytes remains to be defined.

scholarly journals Myocardial intracellular pH in a perfused rainbow trout heart during extracellular acidosis in the presence and absence of adrenaline

1986 ◽  
Vol 125 (1) ◽  
pp. 347-359 ◽  
Author(s):  
A. P. Farrell ◽  
C. L. Milligan
Keyword(s):  
Rainbow Trout ◽  
Intracellular Ph ◽  
Ph Regulation ◽  
Respiratory Acidosis ◽  
Mechanical Efficiency ◽  
Extracellular Ph ◽  
Salmo Gairdneri ◽  
Intracellular Ph Regulation ◽  
Extracellular Acidosis

Myocardial intracellular pH was measured in a perfused rainbow trout, Salmo gairdneri, with DMO (5,5-dimethyl-2,4-oxazlidinedione), to test the hypothesis that catecholamines promote active regulation of myocardial pH in order to protect contractility during a respiratory acidosis comparable to that observed after exercise. Under control conditions (extracellular pH = 8.0; PCO2 = 2 Torr), myocardial pH was 7.53 +/− 0.01 (N = 5). Acidosis (extracellular pH = 7.45; PCO2 = 8.6 Torr) reduced contractility, mechanical efficiency and intracellular pH (7.25 +/− 0.04), but did not affect myocardial O2 consumption. The addition of 0.5 mumol l-1 adrenaline during extracellular acidosis prevented the loss of contractility, restored mechanical efficiency, but did not change intracellular pH significantly. Thus, adrenaline enabled cardiac contractility to recover, without intracellular pH regulation, possibly by modulation of sarcolemmal calcium changes. The absence of a myocardial acidosis after exercise in vivo is discussed with respect to possible intracellular pH regulation via lactate uptake and metabolism.

scholarly journals Mechanism of osmotic activation of Na+/H+ exchange in rat thymic lymphocytes.

1985 ◽  
Vol 85 (5) ◽  
pp. 765-787 ◽  
Author(s):  
S Grinstein ◽  
A Rothstein ◽  
S Cohen
Keyword(s):  
Kinetic Parameters ◽  
Extracellular Ph ◽  
Primary Event ◽  
Exchange System ◽  
Volume Increase ◽  
Regulatory Volume Increase ◽  
Cytoplasmic Acidification ◽  
Stressed Cells

The activity of the Na+/H+ exchange system of rat thymic lymphocytes was determined by means of intracellular (pHi) and extracellular pH (pH0) measurements. In isotonic media, the antiport is virtually quiescent at physiological pHi (7.0-7.1), but is greatly activated by cytoplasmic acidification. At normal pHi, the antiport can also be activated by osmotic shrinking. Osmotic activation occurs after a delay of 20-30 s and is reversed several minutes after iso-osmolarity is restored. The mechanism of activation was analyzed by comparing the kinetic parameters of transport in resting (isotonic) and hyperosmotically stressed cells. The affinities of the external substrate site for Na+ and H+ are not altered in shrunken cells. In contrast, the Hi+ sensitivity of the antiport (which is largely dictated by an allosteric modifier site) was increased, which accounted for the activation. The concentration of free cytoplasmic Ca2+ [( Ca2+]i) increased after osmotic shrinking. This increase was dependent on the presence of extracellular Ca2+ and Na+ and was blocked by inhibitors of Na+/H+ exchange, which suggests that it is a consequence, rather than the cause, of the activation of the antiport. It is concluded that the shift in the pHi dependence of the modifier site of the Na+/H+ antiport is the primary event underlying the regulatory volume increase that follows osmotic shrinkage.

Regulatory volume increase (RVI) and apoptotic volume decrease (AVD) in U937 cells in hypertonic medium

2011 ◽  
Vol 5 (5) ◽  
pp. 487-494 ◽  
Author(s):  
V. E. Yurinskaya ◽  
A. A. Rubashkin ◽  
A. V. Shirokova ◽  
A. A. Vereninov
Keyword(s):  
U937 Cells ◽  
Hypertonic Medium ◽  
Volume Increase ◽  
Regulatory Volume Increase ◽  
Apoptotic Volume Decrease ◽  
Volume Decrease

Response of rainbow trout liver to partial hepatectomy

1993 ◽  
Vol 25 (1-2) ◽  
pp. 31-42 ◽  
Author(s):  
Gary K. Ostrander ◽  
James B. Blair ◽  
Beverly A. Stark ◽  
Jerry G. Hurst
Keyword(s):  
Rainbow Trout ◽  
Partial Hepatectomy ◽  
Rainbow Trout Liver

Secondary regulatory volume increase conferred on Xenopus oocytes by expression of AE2 anion exchanger

1997 ◽  
Vol 272 (1) ◽  
pp. C191-C202 ◽  
Author(s):  
L. Jiang ◽  
M. N. Chernova ◽  
S. L. Alper
Keyword(s):  
Volume Regulation ◽  
Xenopus Oocytes ◽  
Disulfonic Acid ◽  
Functional Coupling ◽  
Intrinsic Volume ◽  
Volume Increase ◽  
Regulatory Volume Increase ◽  
Hypertonic Stimulation ◽  
Shrinkage Prior ◽  
Hypotonic Swelling

Xenopus oocytes lack volume regulation and Cl/anion-exchange (AE) activity but express endogenous Na+/H+ exchange (NHE). We postulated that expression in oocytes of heterologous anion exchangers might allow regulatory volume increase (RVI) via functional coupling with endogenous NHE. Expression of neither erythroid nor kidney isoforms of AE1 conferred any form of RVI. In contrast, although AE2 expression did not confer primary RVI, it did confer on oocytes secondary RVI, with a requirement for hypotonic swelling before hypertonic shrinkage. This secondary RVI required extracellular Cl- and Na+, was blocked by 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid and amiloride, was bumetanide insensitive, and was blocked by prevention of intracellular alkalinization, all properties consistent with functional coupling of AE2-mediated Cl-/HCO3- exchange and endogenous NHE. RVI was unaffected by CO2-HCO3- or by partial oocyte Cl- depletion and was unrelated to the rate of oocyte shrinkage. Prior hypotonic swelling did not significantly alter subsequent hypertonic stimulation of AE2-mediated 36Cl influx or efflux. We conclude that heterologous AE2 expression suffices to confer volume regulation on Xenopus oocytes that lack intrinsic volume-regulatory mechanisms.

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