Effect of activators and inhibitors of K+ - channels on insulin secretion in the pancreas of amphibians.

FRANCINI F.; PIROTTE B; GAGLIARDINO JJ

ARCHIVES OF PHYSIOLOGY AND BIOCHEMISTRY

Año: 1997 vol. 105 p. 66 - 70

1381-3455

The aim of this study was to obtain pharmacological evidence for the presence and participation of K+ channels in amphibian pancreatic islets. Pancreases from the toad Bufo arenarum were thus incubated with activators or blockers of K+ channels and the immunoreactive insulin released into the medium was measured by radioimmunoassay. Two K+-ATP channel openers (diazoxide and BPDZ44) inhibited; while a K+-ATP channel blocker (tolbutamide) and metabolizable sugars (glucose, glyceraldehyde) significantly stimulated the output of insulin. Although a nonmetabolizable sugar (galactose) failed to increase insulin release, dinitrophenol decreased the secretagogue effect of glucose. By contrast, although somatostatin and clonidine blocked the release of insulin, tetraethylammonium significantly stimulated secretion. For each compound tested, the effects on both insulin secretion and B-cell K+ channel activity were similar to those observed in the mammalian pancreas. These findings point to the existence of mammalian-like K+ channels in the B-cells of some amphibians.