Seasonal variation in the active transporting ability and in the membrane ATPase activity of the frog intestinal epithelium.
The active sugar and amino acid transport in the small intestine of the American leopard frog (Rana pipiens) and a species of European frog (Rana esculenta) decreases during the winter months. Parallel with this the (Na+, K+)-stimulated ("pump") ATPase activity is markedly depressed. No seasonal changes are observed in the intestine of the tropical bullfrog (Rana catesbeiana). It is assumed that the low pump-ATPase activity is caused by the hibernation of the frogs living in moderate or subtropical areas and is connected to a biological clock. The decreased active transport of non-electrolytes appears to be a consequence of the change of the ATPase activity.