ENDOTHELIUM-DENUDED PULMONARY RESISTANCE ARTERIES FROM THE FETAL LAMB- PREPARATION AND RESPONSE TO VASOACTIVE AGENTS

A method was developed for preparing endothelium-denuded resistance ar teries (mean internal diameter, 176 mu m) from the term fetal lung to be used for tests in vitro. The endothelium was removed mechanically b y passing a sandpaper-polished cat whisker through the lumen. Ultrastr ucturally, the preparation had a well-preserved internal elastic lamin a which was facing the lumen without any endothelium superimposed. Its response to contractile agents (excess potassium, a thromboxane A(2) analogue, endothelin-1) tended to be greater compared to the intact ar tery. Conversely, the relaxation to acetylcholine was abolished in the endothelium-denuded artery and, in its place, a modest contraction en sued. Sodium nitroprusside relaxation, unlike acetylcholine relaxation , was affected insignificantly by endothelium denudation, This prepara tion, in combination with the preparation of the intact resistance art ery, is a useful, new tool for studying local factors responsible for pulmonary hemodynamic control in utero and through the transitional pe riod at birth.