ANGIOTENSIN-II RECEPTORS AND RENIN IN THE PORCINE UTERUS - MYOMETRIALAT(2) AND ENDOMETRIAL AT(1) RECEPTORS ARE DOWN-REGULATED DURING GESTATION

1. The aim of the present study was to characterize the angiotensin II (AngII) receptor subtypes in the porcine uterus and the variation of receptor densities and renin concentrations during gestation. 2. In my ometrium from non-pregnant sows, the AngII receptors were almost exclu sively AT(2) receptors. During gestation, the AngII receptor density w as decreased and the AT(1) receptor became predominant in the last par t of gestation as a result of a down-regulation of the AT(2) receptor. 3. In the endometrium, the AT(1) receptor was predominant both in non -pregnant sows and throughout gestation, The AngII receptor density wa s decreased during gestation as a consequence of down-regulation of th e AT(1) receptor. 4. The renin concentrations in the myometrium and en dometrium of pregnant sows did not differ from those in non-pregnant a nimals. 5. The finding of enzymatically active renin and high densitie s of AngII receptors in the porcine uterus is in accordance with a fun ctional renin-angiotensin system (RAS), which may be important for an increased vascular permeability and stimulated angiogenesis in early p regnancy and for contraction of the myometrial smooth muscle cells dur ing parturition. The predominance of AT(1) receptors in the endometriu m of non-pregnant sows differs from an earlier finding in non-pregnant women, where AT(2) receptors were predominant in the endometrium. Thi s is in accordance with earlier studies, indicating species difference s in the expression and possibly also the physiological roles of the R AS in reproductive tissues.