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.
Research Article|June 15 1989
Vasopressin-stimulated Ca2+ influx in rat hepatocytes is inhibited in high-K+ medium
A L Savage;
Biochem J (1989) 260 (3): 821-827.
- Views Icon Views
- PDF LinkPDF
- Share Icon Share
- Cite Icon Cite
A L Savage, M Biffen, B R Martin; Vasopressin-stimulated Ca2+ influx in rat hepatocytes is inhibited in high-K+ medium. Biochem J 15 June 1989; 260 (3): 821–827. doi: https://doi.org/10.1042/bj2600821
Download citation file: