Insulin releasing action of 2-[2-(4,5-dihydro-1H-imadazol-2-yl)-1-phenylethyl] pyridine dihydrochloride sesquihydrate (DG-5128), a new, orally effective hypoglycaemic agent.

2-[2-(4,5-dihydro-1H-imidazol-2-yl)-1-phenylethyl] pyridine dihydrochloride sesquilhydrate (DG-5128) is a new orally effective hypoglycaemic agent structurally unrelated to the known hypoglycaemics. DG-5128 was found to decrease blood glucose levels by stimulating insulin release, like the sulphonylurea hypoglycaemics. However, the study with the rat Langerhans islets in vitro indicated a great difference in mode of stimulation of insulin release between DG-5128 and a sulphonylurea hypoglycaemic, tolbutamide. DG-5128 significantly reversed alpha-adrenergic inhibition of the glucose-primed insulin release from the islets, while tolbutamide did not. From the comparison with the effects of phentolamine, yohimbine and prazosine, DG-5128 was strongly suggested to stimulate the glucose-primed insulin release through antagonizing at alpha 2-adrenoreceptors on the B cells.