Reciprocal Distribution of Hexokinase and Glucokinase in the Periportal and Perivenous Zone of the Rat Liver Acinus

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Abstract
Glucokinase and hexokinase activities were measured in the periportal and perivenous zone of the liver acinus separated by microdissection. A microfluorimetric assay was established for the separate determination of both enzyme activities. Glucokinase activity was .apprx. 3.5-fold higher in the perivenous than in the periportal zone in fed male and female rats. After 24 h starvation, this gradient was only slightly changed. Hexokinase showed an inverse gradient with .apprx. 1.5-fold higher activities in the periportal than in the perivenous zone in both fed and fasted animals. Since glucokinase is restricted to parenchymal cells and hexokinase is present predominantly or even exclusively in nonparenchymal cells, the heterogeneous distribution of glucokinase activity supports the model of a metabolic zonation of liver parenchyma with a predominance of glucose uptake in the perivenous and glucose release in the periportal hepatocytes.