The presence of prostacyclin binding sites in nonpregnant bovine uterine tissue

Abstract

Myometrium of various animal species makes a considerable amount of prostacyclin (PGI 2) which is a potent myometrial and uterine vascular smooth muscle relaxing agent. This action of PGI 2 is perhaps mediated by binding to specific receptors, which have never been demonstrated in uterine tissue of any animal species until very recently. The quantitative light microscopic autoradiographic approach used in the present studies demonstrated that while bovine myometrial smooth muscle and uterine vascular smooth muscle contained PGI 2 specific binding sites, endometrial and perimetrial cells contained few or no binding sites. The number of binding sites in circular and elongated myometrial smooth muscle and in arteriolar smooth muscle were similar (P>0.05). The PGI 2 binding to the uterine cells was greatly reduced (P<0.001) following coincubation with excess unlabeled PGI 2, but not with its stable metabolite, 6-keto PGF 1α. PGE 2, PGF 2α and leukotriene C 4 which bind to nonpregnant bovine uterine tissue, also had no effect of PGI 2 binding. In conclusion, nonpregnant bovine uterine tissue contain specific PGI 2 binding sites which may mediate its potent relaxing effect on myometrium and uterine vasculature.