Diabetes, Vol 36, Issue 2 174-178, Copyright © 1987 by American Diabetes Association
Insulin and glyburide increase cytosolic free-Ca2+ concentration in isolated rat adipocytes
B Draznin, M Kao and KE Sussman
We investigated the effect of insulin and a hypoglycemic sulfonylurea agent
glyburide on cytosolic free-Ca2+ concentrations [( Ca2+]i) in isolated rat
adipocytes. Both insulin and glyburide increased [Ca2+]i in a
dose-dependent manner. Half-maximal effects were seen at 0.5 ng/ml of
insulin and 0.5 microM glyburide. Nifedipine (25 microM), a Ca2+-channel
blocker, inhibited the effect of both agents. The effect of insulin on
[Ca2+]i was 40 and 70% potentiated by ambient glucose concentrations at 180
and 300 mg/dl, respectively. Depolarizing doses of potassium (40 mM)
induced an increase in cytosolic Ca2+ that was also inhibited by
nifedipine. It is suggested that both insulin and glyburide increase
cytosolic free Ca2+ levels at least in part by promoting Ca2+ influx
through voltage-dependent Ca2+ channels.