MODULATION OF INSULIN-SECRETION AND CA-45(2+) EFFLUX BY DOPAMINE IN GLUCOSE-STIMULATED PANCREATIC-ISLETS

1. The effect of dopamine on calcium efflux and insulin secretion is examined in the present study. For this purpose, islets isolated from adult Wistar rats were perfused or incubated at 37 degrees C for 60 min. 2. The results obtained from perfused islets indicate that 100 mu M dopamine, in the presence of 5.6 mM glucose, increases insulin secretion and causes a modest elevation of Ca-45(2+) efflux. However, glucose stimuli (from 5.6 to 16.7 mM) provoked an unexpected reduction of insulin release, with no alteration in calcium efflux, when 100 mu M dopamine was present in the perfusion medium. 3. Similar findings were obtained in incubated islets when the prolonged effect of dopamine was investigated. 4. The observations described above led us to conclude that bioactive amines might play an important role in the modulation of the glucose-induced insulin secretion.