ENZYME-HISTOCHEMICAL EVIDENCE FOR THE PRESENCE OF POTENTIAL BLOOD-PRESSURE REGULATING PROTEASES IN CULTURED VILLOUS EXPLANTS FROM HUMAN FIRST TRIMESTER PLACENTAE

The proteases dipeptidyl peptidase IV, angiotensinase A and microsomal alanyl aminopeptidase are present in the human term placenta where th ey may be involved in the local modulation of placental blood pressure . In order to establish an in vitro model system to study the signific ance of these proteases in disorders related to pregnancy-induced hype rtension, the activity of the proteases was localized histochemically in cultured explants of villi from human first trimester placentae. Th ese studies revealed a similar distribution pattern of the activity of the proteases in cryostat sestions of first trimester placental villi and in cultured tissue of the same placentae. Dipeptidyl peptidase IV and angiotensinase A activity were present in cytotrophoblast cells a nd dipeptidyl peptidase IV activity was found in the syncytiotrophobla st, respectively. Additionally, the activity of the proteases was visu alized in various populations of stromal cells. Comparing our results with former studies, the protease activity pattern in first trimester placentae was found to be the same as in term placentae. Despite morph ological changes of the tissue after 14 d in culture the localization of the proteases remainded unchanged up to 52 d of culture. The result s suggest that placental explants may serve as a suitable in vitro mod el for experimental studies on the role of proteases in pregnancy-indu ced hypertension.