The effect of dihydroxy bile acids on intestinal secretion, cyclic nucleotides, and Na+-K+-ATPase

The effects of dihydroxy bile acids on intestinal cyclic nucleotides, Na+-K+-ATPase, and net secretion, and of propranolol pretreatment on these actions were determined. Ileal and colonic loops were constructed in each of 12 rabbits, six of which were treated with propranolol preoperatively. In random order, normal saline, 6mM deoxycholic, chenodeoxycholic, or ursodeoxycholic acids were injected into the intestinal loops. Five hours after, net luminal secretion and mucosal adenylate cyclase, phosphodiesterase, cGMP, and Na+-K+-ATPase were determined. Deoxycholic and chenodeoxycholic acids each increased adenylate cyclase activity (< 0.01) and net secretion (p < 0.01), and decreased cGMP (p < 0.05). Ursodeoxycholic acid did not alter adenylate cyclase activity or secretion but increased cGMP (p < 0.05). Phosphodiesterase and Na+-K+-ATPase were unchanged. Propranolol reversed all of the bile acid effects. In conclusion, chenodeoxycholic and deoxycholic acid induce net intestinal secretion, probably via cAMP. Ursodeoxycholic acid does not affect cAMP but increases cGMP and does not promote net secretion.