Metabolic and secretory response of tumoral-insulin producing cells to D-fructose and D-galactose.

At variance with normal islet cells, tumoral insulin-producing cells of the RINm5F line were found to display a positive secretory response not solely to D-glucose and D-mannose, but also to D-fructose and D-galactose. All hexoses increased the ATP/ADP ratio, exerted a sparing action upon the oxidation of endogenous nutrients in cells prelabelled with either L-[U-14C]glutamine or [U-14C]palmitate, increased the output of lactic acid and, as judged from data collected in the presence of D-[U-14C]hexoses, underwent oxidation in the RINm5F cells. The secretory response to these four hexoses appeared commensurate with the extent of their metabolic effects.