AJP - Cell Physiology, Vol 245, Issue 5 343-C347, Copyright © 1983 by American Physiological Society
Glucose-induced retention of intracellular 45Ca in pancreatic islets
T. Andersson
beta-Cell-rich pancreatic islets from ob/ob mice were loaded with 45Ca in
the presence of 20 mM glucose. When the islets were transferred to a
nonradioactive incubation medium depleted of Ca2+, most of the 45Ca was
lost during the first 10 min of incubation irrespective of whether or not
glucose was present. Isolation of subcellular fractions under conditions
minimizing 45Ca redistribution disclosed that the presence of 20 mM glucose
during the nonradioactive incubation increased the retention of 45Ca in the
mitochondrial fraction. This effect was not reproduced by K+ depolarization
of the islets. Exposure of islets to 4 mM glucose failed to affect the
total content of 45Ca in the islets but increased the incorporation of the
isotope into cellular organelles. These results suggest that glucose, even
at concentrations below the threshold for stimulation of insulin secretion,
enhances the intracellular trapping of calcium.
