Effect of prostanoids on human intestinal Na-K-ATPase activity

To elucidate whether prostanoids affect the activity of human intestinal Na-K-ATPase (an enzyme that has an important role in intestinal sodium and water absorption), basal human jejunal and colonic Na-K-ATPase activities were measured. In normal subjects, the mean (+/- SE) activities were 2.30 +/- 0.20 (n = 18) and 2.06 +/- 0.27 (n = 12) mumol/h . mg protein, respectively. Prostaglandin (PG) E2 (1.3 microM) induced significant inhibition of both the jejunal and the colonic enzyme activities: 82 +/- 5 and 50 +/- 8% inhibition, respectively. The inhibition of the colonic enzyme activity was apparent after 5 min of incubation and was linear in the first 20 min; it correlated with the amount of enzyme protein. PGD2, 6-keto-PGF1 alpha and thromboxane B2 did not affect either the jejunal or colonic Na-K-ATPase activities. These results indicate that PGE2 inhibits intestinal Na-K-ATPase activity. This inhibition may increase intestinal net fluid accumulation and thus may contribute to the diarrhea induced by several prostanoids.