Ultracytochemical localization of adenylate cyclase in early human placenta

Abstract

A cytochemical study was carried out on adenylate cyclase (AC) activity in the early human placenta. Samples of placental villi were incubated in a medium containing adenylyl-imidodiphosphate (AMP-PNP) as specific substrate. No AC reaction product was encountered in placenta villi taken at 5 and 7 weeks of pregnancy. AC activity appeared at 9 weeks. At 9 and 10 weeks, AC reaction product was localized on the basal plasma membranes and on apposed plasma membranes of the Langhans cytotrophoblast. At 11 weeks AC activity was also clearly visible on Langhans cytotrophoblast and syncytiotrophoblast apposed plasma membranes. No AC reaction product was ever detected on the syncytiotrophoblast microvillar membrane. These results are in agreement with biochemical studies that localize AC on the villous trophoblast plasma membranes associated with the fetal circulation.