RESUMO
OBJECTIVE: To study the effect and mechanism of Ca2+ channel blocker on the insulin secretion in islet beta cells of rats. METHODS: The cells were divided into two groups: the low sugar concentration and high sugar concentration groups. These cells were examined with radioimmunoassay and fluorescence method and the effects of nifedipine (NIF), verapamil (VER), and diltiazem (DIL) on the contents of Ca2+ in the islet cells and the secretion volume of insulin at different concentrations were observed. RESULTS: In the low sugar concentration group, NIF, VER and DIL at concentration of 25, 50 and 100 microg/L respectively showed no effect on the contents of Ca2+ in islet cells and the insulin secretion (no statistical significance, P > 0.05). In the high sugar concentration group, these drugs had no inhibitory effect on insulin secretion at concentration of 25 microg/L. However, there was remarkable reduction in Ca2+ contents and insulin secretion when NIF was at the concentration of 50 and 100 microg/L, showing a relationship with dosage (P > 0.05, P > 0.01). VER, when given at 50 microg/L, showed a tendency of reduction in insulin secretion and there was a remarkable reduction at a dosage of 100 microg/L as compared with the control group (P > 0.05). When DIL was given at 100 microg/L, there was a noticeable difference in reduction of insulin secretion as compared with the control group (P > 0.05). CONCLUSION: High dosage of NIF, VER and DIL has an inhibitory effect on the entrance of extracellular Ca2+ into islet cells and thus reduces insulin secretion.