Significance of changes in blood glucose specific activity following insulin administration

¹ Departments of Biochemistry and Medicine, School of Medicine, Western Reserve University, Cleveland, Ohio

Galactose-1-C¹⁴ was administered to dogs receiving a continuous nonradioactive glucose infusion. A rapid rise followed by a gradual decline in plasma glucose specific activity and total activity was observed. However, following insulin administration, while there was an increased disappearance of total counts from the plasma, felt to be a reflection of increased glucose utilization, there was for long periods either a constancy of glucose specific activity, or even a rise in specific activity above preinsulin values. These changes are felt to be consonant only with the entry of glucose of higher specific activity into the circulating blood than that already present. Such glucose presumably could arise from the outer tiers of glycogen formed from galactose during the preinsulin period. The experiments provide experimental proof that cessation of a decline in circulating glucose specific activity following insulin administration need not be interpreted as a cessation of hepatic glucose production.