Sex differences of the influence of T3 on the topical distribution of phosphoenolpyruvate carboxykinase activity in the liver acinus.

Phosphoenolpyruvate carboxykinase (PEPCK) activity was investigated in livers of triiodothyronine (T3) treated male and female rats with special regard to its intraacinar localization. In untreated controls of both, male and female rats, the activity was heterotopically distributed within the acinus with highest values in the periportal zone, and with lowest values in the perivenous zone. This periportal to perivenous activity gradient revealed to be under the influence of T3. Application of T3 resulted in a relative increase of PEPCK activity which was much greater in the livers of females than in males. The extent of T3-induced augmentation of PEPCK activity was dependent on the intraacinar position. In both sexes greatest relative activation was found in the perivenous zone. In female animals, the perivenous activity of T3 treated livers was comparable to that observed in the periportal zone of controls.