Abstract.
Evidence has previously been presented that circadian rhythms play a role in islet hormone secretion. Here, RT-PCR was used to monitor the circadian expression of ether-a-go-go-related gene (Erg) potassium channel isoforms and Erg1 splice variants. Immunohistochemistry was used to identify the pancreatic distribution patterns of ERG1a and ERG1b, as well as ERG2 and ERG3. The influence of ERG on insulin secretion was monitored by perfusion of rat INS-1 β-cells with the blockers E-4031 and rBeKm-1.We identified Erg1a, Erg1b, Erg2 and Erg3 transcripts in islets and INS-1 cells. Immunohistochemistry showed differential expression of ERG isoforms in the islet. Ca2+ imaging and electrophysiological recordings of INS-1 cells during ERG blocking by E-4031 indicated functional ERG channels. Serum shock treatment of INS-1 cells elicited a time-dependent expression response for Erg transcripts. These results add to the current understanding of the function of ERG channels in β-cells and the circadian secretion processes of insulin.
Keywords. Insulin secretion, ERG K+ channel, circadian expression, rat islet function, INS-1 β-cell
Footnotes
Received 8 November 2006; received after revision 1 February 2007; accepted 2 February 2007