Effect of fasting on Na-K-ATPase activity in rat small intestinal mucosa.

The effect of fasting on mucosal Na-K-ATPase activity in various regions of rat small intestine was investigated. Fasting (17--48 h) was associated with a consistent decrease in specific and total activity of Na-K-ATPase in the jejunum, the levels tending to rise more distally. No effect on the specific activities of Mg-ATPase or alkaline phosphatase was found. Fasting was also associated with incresed adrenocortical activity and with decreases in mucosal mass, protein content, and histological dimensions of the jejunum, no similar changes being found in the distal small intestine. Glucose ingestion prevented the decrease in jejunal enzyme activity associated with fasting and elevated levels in the mid and terminal small intestine of fed animals. These effects suggest that Na-K-ATPase activity in small intestinal mucosa may be, in part, inducible.