Abstract
Somatostatin (1 .mu.g/ml) inhibited glucose (16.7 mM)-stimulated 45Ca uptake by isolated rat islets incubated in media containing no added Ca or Ca at a low concentration (0.2 mM). Epinephrine (50 .mu.g/ml) and mannoheptulose (20 mM) inhibited 45Ca uptake by islets incubated in the presence of Ca (0.2 mM). Addition of glucose (16.7 mM) caused a small but significant increase in insulin release from islets incubated in media containing no added Ca. In the presence of a low concentration of Ca (0.2 mM), glucose caused a much greater increase in insulin secretion which was inhibited by addition of somatostatin, epinephrine or mannoheptulose.