The effects and mechanism of islet amyloid polypeptide on insulin secretion in INS-1 cells stimulated by glibenclamide

Abstract

To observe the effects, and study the mechanism of islet amyloid polypeptide (IAPP) on insulin secretion in INS-1 cells stimulated by glibenclamide. Whole cell patch clamp technique was employed to study the influences of short exposure to IAPP on electrophysiological characteristics of ATP-sensitive K+ channel (K(ATP) channel) upon sulfonylurea stimulation. Intracellular free calcium changes in this process was observed by laser scanning confocal microscope. Insulin was measured by enzyme-linked immunoassay. (1) Insulin secretion stimulated by 1 micomol/L glibenclamide was significantly decreased from (11.43 +/- 1.22) microg/L to (9.40 +/- 0.87) microg/L and to (7.11 +/- 1.85) microg/L after 1 micromol/L and 10 micromol/L IAPP incubation, respectively. (2) Glibenclamide-stimulated calcium influx was dose dependently inhibited by IAPP from 1 micromol/L to 10 micromol/L, with the AUC of fluorescence intensity-time reduced from 427.78 +/- 2.32 to 380.59 +/- 1.49, and to 246.53 +/- 8.41, respectively. (3) Compared with that in control cells (14.59 +/- 0.69) mV, the half activation voltage of KA, channel in response to glibenclamide was significantly increased to (28.75 +/- 0.77) mV and to (46.95 +/- 1.81) mV in cells pretreated with 1 micromol/L and 10 micromol/L IAPP, implicating an inhibitory effect of IAPP on activation of K(ATP) channel. Short-term exposure to high concentration of IAPP inhibited glibenclamide-induced closure of K(ATP) channels and decreased calcium influx, which may ultimately lead to the reduction of insulin secretion in INS-1 cells