Influence of bile acids on the (Na+-K+)-activated- and Mg2+-activated ATPase of rat colon.

The influence of various bile acids on the (Na+-K+)-ATPase and Mg2+-ATPase activity of rat colon is described. At a concentration of 0.6 mmol/l C and TC did not inhibit the (Na+-K+)-ATPase activity in contrast to GC. The taurine derivates TC, TCDC and TDC did not influence or even enhanced the (Na+-K+)-ATPase activity. All bile acids except C, TC and CDC depressed the Mg2+-ATPase activity. At higher concentrations only C and TC did not influence the (Na+-K+)-ATPase activity. C, GC and TC at 2.5 mmol/l decreased the (Na+-K+)-activated phosphatase with ATP as substrate. All other substrates tested did not influence the enzymic activity significantly. The results indicate that bile acids can inhibit the Na+-absorbing system in rat colon. Hence this inhibition can cause diarrhea.