Glycolytic isoenzymes and glycogen metabolism in regenerating liver from rats on controlled feeding schedules.

Intact rats trained on a controlled feeding and lighting schedule designated ;8+16' exhibited diurnal oscillations in liver weight, glucokinase activity and liver glycogen content. Glucokinase activity expressed as units/g of liver decreased to 30% of that from unoperated controls during the first 48h after partial hepatectomy and returned to near normal values in 2 weeks. When the glucokinase activity was expressed as units/liver per 100g body wt., a decrease to 50% of control activity was observed between 24 and 48h after the operation. A similar pattern was found for pyruvate kinase type I. In contrast, pyruvate kinase type III activity increased after partial hepatectomy. It is suggested that the newly divided cells after partial hepatectomy do not synthesize glucokinase and pyruvate kinase I but do synthesize pyruvate kinase III. Glycogen was found to accumulate as early as 24h after partial hepatectomy, and normal concentrations were reached after 48h if the operation was performed at times other than during the feeding periods.