scholarly journals Vasopressin-stimulated Ca2+ influx in rat hepatocytes is inhibited in high-K+ medium

1989 ◽  
Vol 260 (3) ◽  
pp. 821-827 ◽  
Author(s):  
A L Savage ◽  
M Biffen ◽  
B R Martin
Keyword(s):  
Plasma Membrane ◽  
Membrane Potential ◽  
Rat Hepatocytes ◽  
Initial Increase ◽  
Phosphorylase Activity ◽  
Plasma Membrane Potential ◽  
Control Value ◽  
High K ◽  
Increased Activity ◽  
Ca2 Channels

We examined the effects of K+ substitution for Na+ on the response of hepatocytes to vasopressin, and on the hepatocyte plasma-membrane potential. (1) High K+ (114 mM) had no effect on the initial increase in phosphorylase a activity in response to vasopressin, but abolished the ability of the hormone to maintain increased activity beyond 10 min. With increasing concentrations a decrease in the vasopressin response was first observed at 30-50 mM-K+. (2) High K+ (114 mM) had no effect on basal 45Ca2+ influx, but abolished the ability of vasopressin to stimulate influx. This effect was also first observed at a concentration of 30-50 mM-K+. (3) Increasing K+ had little effect on the plasma-membrane potential until a concentration of 40 mM was reached. With further increases in concentration the plasma membrane was progressively depolarized. (4) Replacement of Na+ with N-methyl-D-glucamine+ depolarized the plasma membrane to a much smaller extent than did replacement with K+, and was also much less effective in inhibiting the vasopressin response. (5) The plasma-membrane potential was restored to near the control value by resuspending cells in normal-K+ medium after exposure to high-K+ medium. The effects of vasopressin on phosphorylase activity were also restored. (6) We conclude that the Ca2+ channels responsible for vasopressin-stimulated Ca2+ influx are closed by depolarization of the plasma membrane.

scholarly journals Dependence of mammalian putrescine and spermidine transport on plasma-membrane potential: identification of an amiloride binding site on the putrescine carrier

1998 ◽  
Vol 330 (3) ◽  
pp. 1283-1291 ◽  
Author(s):  
Richard POULIN ◽  
Chenqi ZHAO ◽  
Savita VERMA ◽  
René CHAREST-GAUDREAULT ◽  
Marie AUDETTE
Keyword(s):  
Plasma Membrane ◽  
Membrane Potential ◽  
Binding Site ◽  
Biochemical Properties ◽  
Mitochondrial Potential ◽  
Plasma Membrane Potential ◽  
High K ◽  
Polyamine Transport ◽  
Low K

The mechanism of mammalian polyamine transport is poorly understood. We have investigated the role of plasma-membrane potential (ΔΨpm) in putrescine and spermidine uptake in ZR-75-1 human breast cancer cells. The rate of [3H]putrescine and [3H]spermidine uptake was inversely correlated to extracellular [K+] ([K+]o) and to ΔΨpm, as determined by the accumulation of [3H]tetraphenylphosphonium bromide (TPP). Inward transport was unaffected by a selective decrease in mitochondrial potential (ΔΨmit) induced by valinomycin at low [K+]o, but was reduced by ≈ 60% by the rheogenic protonophore carbonylcyanide m-chlorophenylhydrazone (CCCP), which rapidly (≤ 15 min) collapsed both ΔΨpm and ΔΨmit. Plasma-membrane depolarization by high [K+]o or CCCP did not enhance putrescine efflux in cells pre-loaded with [3H]putrescine, suggesting that decreased uptake caused by these agents did not result from a higher excretion rate. On the other hand, the electroneutral K+/H+ exchanger nigericin (10 μM) co-operatively depressed [3H]TPP, [3H]putrescine and [3H]spermidine uptake in the presence of ouabain. Suppression of putrescine uptake by nigericin+ouabain was Na+-dependent, suggesting that plasma-membrane repolarization by the electrogenic Na+ pump was required upon acidification induced by nigericin, due to the activation of the Na+/H+ antiporter. The sole addition of 5-N,N-hexamethylene amiloride, a potent inhibitor of the Na+/H+ antiporter, strongly inhibited putrescine uptake in a competitive fashion [Ki 4.0±0.9 (S.D.) μM], while being a weaker antagonist of spermidine uptake. The potency of a series of amiloride analogues to inhibit putrescine uptake was clearly different from that of the Na+/H+ antiporter, and resembled that noted for Na+ co-transport proteins. These data demonstrate that putrescine and spermidine influx is mainly unidirectional and strictly depends on ΔΨpm, but not ΔΨmit. This report also provides first evidence for a high-affinity amiloride-binding site on the putrescine carrier, which provides new insight into the biochemical properties of this transporter.

Effect of glucagon on hepatic taurocholate uptake: relationship to membrane potential

1985 ◽  
Vol 249 (4) ◽  
pp. G427-G433
Author(s):  
J. W. Edmondson ◽  
B. A. Miller ◽  
L. Lumeng
Keyword(s):  
Plasma Membrane ◽  
Bile Acid ◽  
Membrane Potential ◽  
Rat Hepatocytes ◽  
Isolated Hepatocytes ◽  
Hill Coefficient ◽  
Isolated Rat Hepatocytes ◽  
Plasma Membrane Potential ◽  
Sodium Dependent

Since glucagon can hyperpolarize hepatic plasma membrane and stimulate biliary bile acid secretion in vitro, we studied the effect of glucagon on taurocholate uptake and its relationship to plasma membrane potential in isolated rat hepatocytes. [14C]taurocholate uptake was linear through 1 min and contained a saturable sodium-dependent and a nonsaturable sodium-independent component. Km of taurocholate uptake by the sodium-dependent system was 18.4 microM. Hill coefficient for Na+ was 2.59 and for taurocholate was 1.1, suggesting that the stoichiometry is 2 Na+:1 bile acid. Stimulation of taurocholate uptake by glucagon was limited to the sodium-dependent component, detected within 5 min of hormone exposure, and was maximum at 30 min. Glucagon, from 10(-8) to 10(-5) M, stimulated taurocholate uptake and hyperpolarized concurrently the plasma membrane potential. Because valinomycin produced a dose-related depolarization of plasma membrane potential, this agent was used to counteract the effects of glucagon. With 10(-6) M glucagon, valinomycin (10(-10) M) depolarized membrane potential from -35.50 to -28.00 mV and inhibited taurocholate uptake from 60% above the control rate to 5% below. These data strongly suggest that taurocholate uptake by isolated hepatocytes is an electrogenic process, and its stimulation by glucagon may be mediated by changes in plasma membrane potential.

Calcium modulation of exocytosis-linked plasma membrane potential oscillations in INS-1 832/13 cells

2015 ◽  
Vol 471 (1) ◽  
pp. 111-122 ◽  
Author(s):  
Akos A. Gerencser ◽  
Hindrik Mulder ◽  
David G. Nicholls
Keyword(s):  
Plasma Membrane ◽  
Membrane Potential ◽  
Oscillation Frequency ◽  
Potential Oscillations ◽  
Plasma Membrane Potential ◽  
K Channels ◽  
Calcium Modulation ◽  
Membrane Potential Oscillations ◽  
Ca2 Channels

Oscillations in plasma membrane potential initiated by substrate-dependent blockade of ATP-sensitive K+ channels in insulin-secreting INS-1 832/13 are differentially linked to distinct voltage-activated Ca2+ channels and drive exocytosis. Ca2+ feeds back to control oscillation frequency, amplitude and prevalence.

scholarly journals TRPC6 regulates phenotypic switching of vascular smooth muscle cells through plasma membrane potential‐dependent coupling with PTEN

2019 ◽  
Vol 33 (9) ◽  
pp. 9785-9796 ◽  
Author(s):  
Takuro Numaga‐Tomita ◽  
Tsukasa Shimauchi ◽  
Sayaka Oda ◽  
Tomohiro Tanaka ◽  
Kazuhiro Nishiyama ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Plasma Membrane ◽  
Membrane Potential ◽  
Vascular Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Vascular Smooth Muscle Cells ◽  
Muscle Cells ◽  
Phenotypic Switching ◽  
Plasma Membrane Potential

scholarly journals Kinetic study of the plasma-membrane potential in procyclic and bloodstream forms of Trypanosoma brucei brucei using the fluorescent probe bisoxonol

1996 ◽  
Vol 314 (2) ◽  
pp. 595-601 ◽  
Author(s):  
Fabienne DEFRISE-QUERTAIN ◽  
Chantal FRASER-L'HOSTIS ◽  
Danièle CORAL ◽  
Jacques DESHUSSES
Keyword(s):  
Plasma Membrane ◽  
Membrane Potential ◽  
Trypanosoma Brucei ◽  
Cultured Cells ◽  
Bloodstream Form ◽  
Metabolic Inhibitors ◽  
Trypanosoma Brucei Brucei ◽  
Plasma Membrane Potential ◽  
Regulation Mechanisms ◽  
K Concentration

The characteristics of the plasma-membrane potential of procyclic and bloodstream forms of Trypanosoma brucei brucei (cultured cells) were investigated using the fluorescent anionic probe bisoxonol. Observation of a stable and representative plasma-membrane potential in the resting state required careful washing, centrifugation and maintenance of the cells at room temperature before measurement. Bloodstream forms were more prone to depolarization during washing at 4 °C than procyclic cells. The higher fluorescence observed in the presence of long slender cells than in the presence of procyclic cells shows that the plasma-membrane potential is more negative in the insect form. Healthy dilute cells can sustain their plasma-membrane potential for hours in the presence of external glucose. The presence of a high K+ concentration in the medium did not promote by itself the depolarization of either type of cell. Study of bisoxonol fluorescence as a function of time allowed us to follow the kinetics of the action of metabolic inhibitors in the presence of various ions. o-Vanadate (1 mM) was found to depolarize bloodstream-form cells rapidly but only in a phosphate-free NaCl buffer. Omeprazole and strophanthidin also specifically depolarized bloodstream-form trypanosomes. However, NN´-dicyclohexylcarbodi-imide depolarized both types of cell, but more rapidly for bloodstream-form cells. Bloodstream-form trypanosomes appear to use mainly a vanadate-sensitive Na+ pump to maintain their Na+-diffusion gradient. However, most of the ATPase inhibitors tested had little or no effect on the plasma-membrane potential of procyclics suggesting that this form of trypanosome may rely on several regulation mechanisms.

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