Original Article: PDF OnlyUnclipping of two-kidney, one clip hypertensive rats produces endothelium-dependent inhibition of sympathetic vasoconstrictionGerkens, John F. Author Information From the Discipline of Clinical Pharmacology, University of Newcastle, Newcastle, NSW 2300, Australia Journal of Hypertension: December 1989 - Volume 7 - Issue 12 - p 961-966 Buy Abstract Removal of the renal artery-constricting clip in two-kidney, one clip (2-K.1C) Goldblatthypertensive rats produces a rapid fall in blood pressure which has been attributed to the release of vasodepressor lipids from the renal medulla. The aim of this study was to demonstrate the effect of unclipping 2-K,1C hypertensive rats, and of any hormone thereby released, on vasoconstrictor responses to sympathetic stimulation in the ex vivo bloodperfused tail artery, as well as the role of the vascular endothelium in mediating this effect. Blood was withdrawn at a rate of 2ml/min from the carotid artery of an anaesthetized 2-K,1C rat and used to perfuse, via an extracorporeal circuit, a cannulated segment of tail artery which had been taken from a killed, normal rat and mounted in an organ bath. The blood was returned to the 2-K,1C rat via the jugular vein. Vasoconstriction and increases in perfusion pressure were produced by periarterial electrical stimulation of the tail artery. The tail artery was either intact or had had its endothelium removed. Sham operations which did not remove the renal artery clip did not change blood pressure or vasoconstrictor responses. Unclipping lowered blood pressure and reduced vasoconstrictor responses in ex vivo blood-perfused tail arteries in which the endothelium was intact, but did not decrease responses in tail arteries from which the endothelium had been removed. It is concluded that unclipping releases a hormone which lowers blood pressure and inhibits sympathetic vasoconstrictor responses via an endothelium-dependent mechanism. © Lippincott-Raven Publishers.
