Production of Chorionic Somatomammotropin (oCS), Fetal Growth and Growth of the Placenta and the Corpus Luteum in Ewes Treated with 2-Bromo-α-Ergocryptine*

Abstract

Forty ewes treated with bromocryptine (2-bromo-α-ergocryptine) from midgestation onward were compared with 52 control ewes. RIA for PRL revealed that the treated ewes were severely hypoprolactinemic. No modification of the concentrations of ovine chorionic somatomammotropin (oCS) in blood (as determined by radioreceptor assay) occurred with this treatment at any gestational stage; however, between 80 and 100 days of pregnancy, placental oCS concentrations increased four to six times [136 ± 6 μg/g fresh tissue wt (n = 6), as compared with 22 ± 5 μgg/g fresh wt (n = 12), P < 0.001]. Maximal placental oCS levels occurred 1 month earlier (80–85 days) in the treated animals and were twice those of untreated animals (70 ± 5 μgg/g fresh wt, n = 13 at 110–120 days, P < 0.001). From 110–120 days of pregnancy onwards, placental oCS concentrations in treated animals dropped to control levels. Placental and fetal growth as well as oCS and PRL levels in fetal blood were not modified by maternal hypoprolactinemia. Up to 140 days of pregnancy, the weight of the gestational corpus luteum decreased by 14%, but this decrease was highly significant (703 ± 24 mg, n = 32 in the controls; 607 ± 18 mg, n = 38 in the treated ewes; P < 0.01), although it is known that both PRL and LH are necessary to maintain the cyclic corpus luteum in the ewe. It is suggested, first that oCS biosynthesis may depend on some kind of endocrine control and second, that gestational corpora lutea may be maintained, at least in part, by a placental luteotrophic complex.