Metabolic and secretory interactions between D-glucose and D-fructose in islets from GK rats

The metabolism of D-glucose and/or D-fructose was investigated in both panc reatic islets and parotid cells of control and hereditarily diabetic Goto-K akizaki (GIC) rats. In the islets from GK rats, a preferential alteration o f the oxidative response to D-glucose coincided with an impaired secretory response to the aldohexose. Such a metabolic alteration was not found in th e parotid cells of GK rats. Whether in islet or parotid cells, D-fructose L ittle affected the catabolism of glucose in either control or GK rats. The metabolism of D-fructose and the effect of D-glucose thereupon were essenti ally comparable in control and GK rats in both pancreatic islets and paroti d cells. In both cell types, the comparison between the metabolism of D-glu cose and D-fructose in cells simultaneously exposed to the two hexoses sugg ested a far from negligible contribution of fructokinase to the phosphoryla tion of D-fructose. Although the catabolism of the ketohexose and its modul ation by D-glucose were closely comparable in islets from control and GK ra ts, the insulinotropic action of the ketohexose, relative to that of the al dohexose, was severely impaired in the GK rats. The present work thus empha sizes the specificity of the alteration in D-glucose metabolism in islets, as opposed to extrapancreatic cells, of GK rats. It also reveals in the isl ets of GK rats a further secretory anomaly apparently not attributable to t he impairment of nutrient catabolism in the islet cells of these diabetic a nimals.