Effect of manno-heptulose on glucose kinetics in normal and gluco-corticoid treated dogs

The hepatic glucose output (Ra) was measured in dogs with indwelling arterial and venous catheters, using 2-³H-glucose as tracer according to the primed constant rate infusion technique. From the rate of disappearance of glucose and plasma glucose level the clearance rate (CR) was calculated. 1.2-1.5 g/kg manno-heptulose was given i.a. to control and methylprednisolone (MP) treated dogs. Plasma insulin (iRi) decreased and the resulting hyperglycemia was clearly caused by the sharp rise of Ra. A decrease of CR seemed to be responsible for the slow return of plasma glucose. Plasma FFA and lactate did not show marked changes. As iRi decreased plasma cAMP rose. MP treatment greatly (3.5 fold) potentiated the effect of MH on hepatic glucose output. It was concluded that the diabetogenic effect of MH was due to the excess breakdown of liver glycogen caused by the inhibition of insulin release and presumably by the increase of glucagon release as shown by others.