Vascular Smooth Muscle Reactivity and Endothelium Derived Relaxing Factor in Experimental Obstructive Jaundice

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Abstract
Obstructive jaundice is associated with a predisposition to systemic hypotension and acute renal failure. Altered vascular reactivity may contribute to the development of hypotension. In this experimental study on dogs, alterations in vascular contractile responses to noradrenaline, serotonin and KCl were investigated. Contractile responses to noradrenaline, serotonin,,, KCL and relaxation responses to papaverin and acetylcholine were provoked in isolated femoral arteries of both control dogs and animals with obstructive jaundice. In this situation concentration-response curves of noradrenaline and serotonin were blunted when compared with controls. This blunting disappeared when endothelium was removed. In rings precontracted with phenylephrine, EDRF relaxation responses to acetylcholine were increased significantly as compared to controls: at lower concentrations maximal relaxation response occurred. Contractile responses to KCl and relaxation responses to papaverin did not differ between the groups, endothelium present or removed. These results indicate that obstructive jaundice induces a decrease in vascular contractile responses and an increased EDRF relaxation response. We suggest that an excess in the amount of released EDRF may be one of the causes inducing systemic hypotension in obstructive jaundice.