MECHANISM OF PREGNANCY-INDUCED ATTENUATION OF CONTRACTION TO PHENYLEPHRINE IN RAT AORTA

The role of endothelium in the decreased contraction to phenylephrine in aorta of pregnant Wistar rats has been studied. Contractions in res ponse to phenylephrine were significantly decreaSed in aortic rings fr om pregnant rats compared to those from non-pregnant rats. Pretreatmen t of the rings with indomethacin did not significantly alter the patte rn of responses. When endothelium was removed from the rings, contract ions of rings from non-pregnant rats were similar to those from pregna nt rats. Acetylcholine-induced relaxations of rings from pregnant and non-pregnant rats precontracted with phenylephrine were not significan tly different. The results suggest that in the rat aorta and under in vitro conditions, pregnancy-induced attenuation of contraction to phen ylephrine is, at least partly, endothelium dependent and that the rele ase of the endothelium factor responsible for this alteration in respo nse may be indomethacin insensitive.