AbstractsBiology & Animal Science

Livers from rats fasted 48 hours or rats bearing the ascitic form of Novikoff hepatoma have an increased Mg++ or Ca++ - stimulated ATPase activity. Mg++ - Na+ - K+ - stimulated ATPase activity is not affected by the two conditions either in level of ATPase activity or with respect to the interaction of Na+ and K+. The elevated liver ATPase activity is inversely related to the glycogen content. Conditions which deplete liver glycogen such as starvation, glucagon injection, in vitro incubation or the presence of the ascitic form of Novikoff hepatoma, results in an increase in the Mg++ - stimulated ATPase activity. The re-synthesis of glycogen also shows a correlation with ATPase activity. Re-feeding a 48-hour fasted animal for 24 hours with sucrose returns both glycogen and ATPase activity to fed animal levels. Glucose injections over a 4 hour period results in an increase in the glycogen content up to 30% of that found in fed animals and a 50% decrease in the increased ATPase activity.