Influence of the oral hypoglycemic agent linogliride (McN-3935) on insulin secretion from isolated rat islets of Langerhans

The influence of a new orally effective hypoglycemic compound, linogliride (McN-3935), on Insulin release from isolated perifused rat islets was investigated. At a concentration of 100 microM, linogliride was without effect on Insulin secretion in the absence of glucose. While 5.5 mM glucose alone produced a weak secretagogue effect, the secretory response was dramatically (5- to 6-fold) increased by the addition of 100 microM linogliride. This concentration of linogliride did not affect the conversion of [5-3H]glucose to 3H2O, a measure of the rate of glycolysis by the islet. Insulin secretion in response to the combination of 100 microM linogliride and 5.5 mM glucose was abolished by the omission of extracellular calcium. Mannoheptulose (10 mM), an inhibitor of glucose phosphorylation and glucose-stimulated Insulin secretion, markedly attenuated the insulinotropic effect of linogliride in parallel with reduced glucose usage. Paradoxically, in the presence of another metabolic inhibitor, 2-deoxyglucose (10 mM), the insulinotropic effect of linogliride (100 microM) in the presence of 5.5 mM glucose was not diminished despite the reduced glucose usage. Linogliride significantly increased the secretory response to other secretagogues, including 2.5 mM D-glyceraldehyde, 15 mM N-acetylglucosamine, 10 mM leucine, and 100 nM of the phorbol ester 12-O-tetradecanoylphorbol-13-acetate. These data suggest that linogliride amplifies a cellular signal generated during beta-cell activation by various stimulants.