Role of TRPM5 channel in insulin secretion from rat β-cells

Objectives: Several studies have reported that the Transient Receptor Potential Melastatin-like subtype 5 (TRPM5) channel, a Ca activated monovalent cation channel, is involved in the stimulus secretion coupling in the mouse pancreatic β-cells. We have studied the role of the TRPM5 channel in regulating insulin secretion, and cytoplasmic free Ca concentration ([Ca]i) in the rat β-cells by using triphenyl phosphine oxide (TPPO), a selective inhibitor of the channel. Methods: Insulin secretion from islets from Sprague-Dawley rats were measured in batch incubations. [Ca]i was measured from single β-cells by Fura-2 based microfluorometry. Results: TPPO did not alter insulin secretion and [Ca]i response triggered by KCl, or fructose. It inhibited insulin secretion in response to glucose, L-Arginine, and GLP-1. It also inhibited the KATP channel-independent insulin secretion, and [Ca]i increase by glucose. Conclusions: Our results suggest that in the rat islets, TRPM5 is involved in mediating insulin secretion by glucose, L-Arginine, and in potentiating the glucose-induced insulin secretion by GLP-1.