Effects of islet amyloid polypeptide on electrophysiological characteristics of KATP channel in rat islet cell tumor cell line Ins-1

Abstract

Objective To observe the effects of islet amyloid polypeptide (IAPP) on KATP channel in rat islet cell tumor cell line Ins-1 stimulated by high concentration of glucose. Methods Ins-1 cells, as the research object, were randomly divided into 16.7 mmol/L glucose control group and 0.1, 1, 10 μmol/L amylin pretreatment group. Whole cell patch clamp technique was employed to study the influences of short exposure to IAPP on electrophysiological characteristics of KATP channel upon glucose stimulation. Meanwhile, insulin secretion was measured by enzyme-linked immunoassay. Group data were compared by using t test with the P value set at 0.05. Results The insulin secretion and half-maximal activation voltage (V0.5) of KATP in cells incubated with 16.7 mmol/L glucose were (5.57±0.93) μg/L and (9.4±1.4) mV, respectively; and those were (4.95±0.49)μg/L and (13.0±2.4) mV in cells pretreated with 0.1 μmol/L amylin; and there was no significant differences between the two groups(t=1.022, -2.244, both P>0.05). While the insulin secretion in cells pretreated with 1 μmol/L and 10 μmol/L amylin significantly decreased ((3.44±0.32)μg/L and (2.23±0.55) μg/L, respectively) and the V0.5 increased significantly((28.2±2.7) mV and (33.3±2.1) mV, respectively) when compared with those in cells treated with 16.7 mmol/L glucose (t=3.751, 5.354, -5.053, -10.707, all P<0.05). Conclusions Short-term exposure to high concentration of amylin inhibites the closure of ATP-sensitive potassium channels upon glucose stimulation, thus may ultimately lead to the reduction of insulin secretion in Ins-1 cells. Key words: Islet amyloid polypeptide; Rat islet cell tumor cell line Ins-1; ATP-sensitive potassium channels