The localization and expression of the renin-angiotensin system in the human placenta throughout pregnancy

All the components of the renin-angiotensin system (RAS), including the AT(1) receptor, have previously been shown to be present in the human term placenta. However, the presence of the RAS components has not been fully investigated in the human placenta throughout pregnancy. The aim of this study was to examine the localization of the angiotensin receptors AT(1) and AT(2) using immunocytochemistry and the expression of prorenin, angiotensinogen and the AT(1) and AT(2) receptor mRNA using RT-PCR in the human placenta in the first, second and third trimesters of pregnancy. Localization of the AT(1) receptor was shown throughout gestation in the syncytiotrophoblast, cytotrophoblast, Hofbauer cells and the fetal vascular endothelium. Expression of mRNA for prorenin, angiotensinogen and the AT(1) receptor was shown in the placenta throughout gestation. However, localization or mRNA expression of the AT(1) receptor was not detected in any of the placental samples studied. These results clearly show the expression of a majority of the components of the RAS in the placenta from early gestation onwards. Therefore, these results suggest that the RIS may have a role in the human placenta throughout gestation. (C) 1999 W. B. Saunders Company Ltd.