Effects of fetal sex, stage of gestation, dibutyryl cyclic adenosine monophosphate, and gonadotropin releasing hormone on secretion of human chorionic gonadotropin by placental explants in vitro.

Explants from 16 term and 6 midtrimester placentas were cultured for 6 days. Statistically significant increases in secretion of human chorionic gonadotropin occurred in control medium cultures of both term and midtrimester explants during the 6-day culture period (p less than 0.01). Statistically significant increases in secretion of human chorionic gonadotropin were produced by 2 mmol/L dibutyryl cyclic adenosine monophosphate in both the term (p less than 0.01) and the midtrimester (p less than 0.01) explants. There was no effect of gonadotropin releasing hormone. The ratio of human chorionic gonadotropin secretion from midtrimester explants to that from term explants varied under different conditions, dropping from twentyfold in day 1 cultures to elevenfold for maximum secretion produced after culture in control medium for up to 6 days. A further drop in the ratio to fourfold was observed for the maximal response to 2 mmol/L dibutyryl cyclic adenosine monophosphate treatment. Explants from term female infants produced significantly more human chorionic gonadotropin than those from term male infants (p less than 0.05), but the sex difference disappeared after stimulation with 2 mmol/L dibutyryl cyclic adenosine monophosphate.