Effect of circulatory disturbance on the activities of rate-limiting enzymes of carbohydrate metabolism in rar liver

Studies on the rats with ligation of the portal vein branch

Abstract

Activities of rate-limiting enzymes of carbohydrate metabolism in rat liver were determined following the ligation of a portal vein branch and compared with those in sham-operated and control rats.
In the ligated liver lobes, the activities of liver specific glucose 6-phosphatase (G6Pase), fructose 1, 6-diphosphatase (FDPase) and glucokinase (GK) were markedly decreased, while the activities of hexokinase (HK), glucose 6-phosphate dehydrogenase (G6PDH) and pyruvate kinase Type M₂ (PK-M₂), which are non-specific to the liver, were increased considerably. In the non-ligated lobes, G6Pase, GK and pyruvate kinase Type L (PK-L) activities were low and HK, G6PDH and PK-M₂ were high; however, extents of the changes were much less than in the ligated lobes. The decreased activities of G6Pase, FDPase and GK in the ligated lobes persisted as far as 21 days after ligation, suggesting that the changes were due to the liver cell atrophy or change in cell population after deprivation of the portal blood rather than to the liver cell necrosis or hyperplasia.
The consequence of these changes in the rate-limiting enzyme activities is the depression of liver specific functions, and the phenomenon could be interpreted as an adaptation of ligated and non-ligated liver lobes to the unfavorable conditions with diminished blood supply.