It was found previously that in normal dogs D-glucose or D-(-)-ribose decrease the rate of endogenous (hepatic) glucose production. To investigate whether this effect is due to the release of extra insulin only, or to other factors as well, the following experiments were performed: Endogenousinsulin secretion was replaced by intraportal porcine or canine insulin infusion of 200 μU./kg./min. in conscious dogs. Such an insulin infusion commenced at time of removal of the remnant pancreatic autograft was able to maintain unchanged the plasma glucose level and the tracer determined glucose production and utilization. Three main conclusions emerged from this study: (1) Since an infusion of D-(-) -ribose did not affect concentration and turnover rates of glucose, it was concluded that ribose affects glucose metabolism only through an increase of the rate of insulin secretion. (2) The endogenous glucose production did not decrease in response to a glucose infusion at two thirds to twice the basal normal glucose production, even when the concentration of glucose in plasma exceeded 200 mg./100 ml. It is concluded that the release of extra insulin is indispensable for the regulation of glucose production in the normal dog. (3) The utilization of glucose rose in proportion to its concentration in the plasma in the absence of any change in the rate of insulin supply.

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