Action of renal vasodilators in dogs following acute biliary obstruction

The renal vasodilator properties of six endogenous substances were tested before and 4 hr after ligation of the common bile duct. Two substances, acetylcholine and a glucocorticoid, retained their vasodilator properties at a fixed dose following acute biliary obstruction. Dopamine was still able to increase glomerular filtration rate and renal blood flow, but demonstrated an attenuated response. Several other agents, glucagon, glycine, and bradykinin, lost their renal vasodilator actions at the dosages employed. For these latter three compounds, control studies using sham-obstructed dogs and identical waiting periods demonstrated no loss of vasoactive effect. When the order of experimental protocol was reversed, i.e., acute biliary obstruction followed by a 4-hr period without obstruction, the same phenomenon was observed. When dogs were tested 5 days following biliary obstruction, glycine, glucagon, dopamine, and dexamethasone all failed to raise either GFR or renal perfusion. The infusion of bile or dialyzed bile, but not bile salts or bilirubin, also caused the failure of glucagon, glycine, and bradykinin to exert a renal vasoactive effect. Dogs with 4 hr of biliary obstruction appeared to react normally to the pressor effects of noradrenaline and angiotensin II and to the diuretic effects of iv furosemide. The obstruction of the bile ducts with percolation of bile constituents into the circulation appears to alter the sensitivity of the renal vasculature to certain endogenous vasoactive agents.