Regional distribution of Na-K-ATPase specific activity in the large intestine of the rat and man.

Segmental heterogeneity of colonic electrolyte transport has been demonstrated in rat and man. We determined whether this is reflected by regional differences in Na-K-ATPase activity. In rats, Na-K-ATPase specific activity was significantly lower in the caecum than in the proximal colon, distal colon, and rectum. In man, biopsy specimens of macroscopically intact mucosa in 26 subjects showed no difference in Na-K-ATPase specific activity along the colon axis. We conclude that Na-K-ATPase distribution may contribute to electrolyte transport differences between rat caecum and colon but not between colonic segments in either rat or man. In an additional series of 11 patients with proximal intestinal resections colonic Na-K-ATPase specific activity was slightly but significantly higher than in controls, possibly representing an adaptive process.