AJP - Endocrinology and Metabolism, Vol 243, Issue 3 196-E205, Copyright © 1982 by American Physiological Society
Nutrient-induced intracellular calcium movement in rat pancreatic B cell
P. Lebrun, W. J. Malaisse and A. Herchuelz
Several insulin secretagogues increase 45Ca efflux from islets prelabeled
with the tracer in the presence of glucose, an effect attributable to
stimulation of 40Ca entry into islet cells. When the islets are prelabeled
in the absence instead of presence of glucose, the 45Ca becomes more
readily releasable, and the secretory response to nutrient or ionic
secretagogues is decreased. Such a decrease is more marked in response to
glucose than other secretagogues because the prior nutrient deprivation
also impairs the metabolism of glucose in islet cells. In the islets
prelabeled in the absence of glucose, both glyceraldehyde and
2-ketoisocaprote dramatically stimulated 45Ca efflux. This effect persists
in the absence of extracellular Ca2+ or presence of the
calmodulin-antagonist trifluoperazine. It may correspond to a
nutrient-induced intracellular Ca2+ movement, the existence of which would
be unmasked in islets prelabeled in the absence of glucose. This
so-far-undetected Ca2+ movement may play a role in the secretory response
to nutrient secretagogues.
