| Abstract: | Staining procedures for glucose-6-phosphatase and 3-hydroxybutyrate dehydrogenase activity and for glycogen were used to investigate adaptive changes in the regionality of hepatic gluconeogenesis and ketogenesis in fasting male and female rats. A reciprocal distribution of gluconeogenic and ketogenic capacities was found in both sexes, but male and female animals were different with respect to: a) the time necessary for full induction of glucose-6-phosphatase activity (24 h in females, 48 h in males); b) the overall activity of 3-hydroxybutyrate dehydrogenase; and c) glycogen content. The activity of the latter enzyme and the glycogen content did increase with time of starvation, but at all times, were higher in males, than in females. Results, thus, indicate that the extent to which ketone bodies replace glucose as major fuel for the brain is larger in males than in females. This may explain the delayed induction of glucose-6-phosphatase activity and the higher glycogen content in the male during starvation. Distributions of enzyme activities and of glycogen, furthermore, revealed the heterogeneity of the lobular periphery, i.e. functional differences among sinusoids dependent upon whether they originate from the portal tract or the vascular septum, and thus confirm the lobular concept proposed by Matsumoto et al. (1979). |
