English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Zendy Plus

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Zendy Tools

Zendy Open

It is well established that the human placenta provides the main source of progesterone after the first trimester of pregnancy. This progesterone is thought to be synthesized mainly from cholesterol present in the maternal circulation (Diczfalusy, 1969). However, little is known of the factors which control placental progesterone synthesis. The present work was carried out to see whether various hormones, and other compounds which affect steroidogenesis in other tissues, had any effect on the conversion of cholesterol to progesterone by the human placenta in vitro. The substances investigated were HCG, ovine prolactin (LTH), prostaglandin E1, which stimulates ovarian steroidogenesis in various species (Speroff & Ramwell, 1970; Kuehl, Humes, Tarnoff, Cirillo & Ham, 1970) and which activates human placental adenyl cyclase (Satoh & Ryan, 1972), adrenaline, another compound which increases placental adenyl cyclase activity (Satoh & Ryan, 1971), vasopressin, which increases plasma progesterone levels in pregnant women (Fylling, 1971), and cyclic-AMP, the proposed second messenger mediating the effects of steroidogenic hormones in other tissues. The effects of prostaglandin F2(I, which has been detected in amniotic fluid and maternal blood during labour (Karim & Devlin, 1967; Karim, 1968) were also investigated. This compound is effective in inducing labour (Karim, Trussell, Hillier & Patel, 1969) and it was considered that an inhibitory effect on placental progesterone synthesis might contribute to this action. Fresh post-partum placentae were obtained from a local maternity hospital. After birth, the placenta was placed in a beaker containing cold saline and transported to the laboratory with the minimum of delay. Small pieces were taken randomly from the placenta and cut into 200-μ slices with a Mcllwain tissue chopper. The pooled slices were distributed among incubation flasks containing 20 ml Krebs' phosphate buffer, pH 7-4, to which had been added human serum albumin (250 μg/ml), glucose-6-phosphate (4 mM) and NADP (0-65 mM or 0-25 min). The medium also contained [7oc-3H]cholesterol (0-09 to 0-45 μ / ), previously purified by thin-layer chromatography and dissolved in propylene glycol (1 ml/100 ml incubation medium). The various test substances were added to the appropriate flasks.

EFFECTS OF HORMONES, PROSTAGLANDINS AND CYCLIC-AMP ON THE SYNTHESIS OF PROGESTERONE BY THE HUMAN PLACENTA IN VITRO