Hormonal factors affecting glucose 6-phosphatase activity. 2. Some effects of diet and of alloxan diabetes in the rat

Abstract

In the intact rat starvation for 24 hr. caused a rise in liver glucose 6-phosphatase concentration but relatively little change in the total glucose 6-phosphatase activity of the liver. This confirms the previous findings of others. When the rat was allowed to eat glucose ad libitum after being starved for 24 hr. the liver glucose 6-phosphatase concentration fell almost to the value seen in the normal animal. The changes in enzyme activity observed in the starved rat and in the rat fed with glucose after starvation for 24 hr. were apparent rather than real and can be satisfactorily explained as a result of changes in liver size and composition. When the rat was allowed to eat fat or casein ad libitum after starvation for 24 hr. the glucose 6-phosphatase activity/100 g of liver was the same as that of the starved animal. However, there was a small but significant rise in the total liver glucose 6-phosphatase activity/100 g body wt. when the starved rat was fed with fat and a highly significant rise when it was fed with protein. Alloxan diabetes caused a rise in liver glucose 6-phosphatase activity, as had been reported previously, and also a rise in kidney glucose 6-phosphatase activity. The view is put forward that if sufficient protein is available, liver glucose 6-phosphatase activity in the rat rises in response to a deficiency of exogenous glucose.