AJP - Endocrinology and Metabolism, Vol 258, Issue 3 E529-E533, Copyright © 1990 by American Physiological Society
Sensitivity to Cd2+ but resistance to Ni2+ of Ca2+ inflow into rat pancreatic islets
P. O. Plasman, M. Hermann, A. Herchuelz and P. Lebrun
Laboratory of Pharmacology, Brussels Free University, School of Medicine, Belgium.
The presence of different types [long lasting (L) and transient (T)] of
active voltage-operated Ca2+ channels in islet cells was investigated by
comparing the effects of Cd2+, Ni2+, and 1,4-dihydropyridines on 45Ca
uptake, 45Ca efflux, and insulin release in intact rat pancreatic islets.
In several other excitable cells the L-channel has been shown to be
modulated by 1,4-dihydropyridines and Cd2+, whereas the T-channel was
reported to be sensitive to Ni2+. Nifedipine and Cd2+ inhibited whereas BAY
K 8644 enhanced the glucose (11.1, 22.2 mM)-stimulated short-term 45Ca
uptake, 45Ca efflux, and insulin release. In contrast, the stimulatory
effects of glucose (11.1, 22.2 mM) on 45Ca uptake, 45Ca efflux, and insulin
release were unaffected by Ni2+. These findings confirm that glucose
provokes Ca2+ entry mainly by activating voltage-sensitive Ca2+ channels of
the L-type and suggest that the B-cell plasma membrane is not equipped with
active T-type Ca2+ channels.
