Placentation in the African elephant,

Placental and fetal tissues were recovered from the uteri of 59 pregnant elephant that ranged in estimated age from day 1 B to month 21 of gestation. Incubation of placenta and fetal gonad, alone or in combination, with tritium-labelled cholesterol, pregnenolone and androstenedione failed to yield any labelled progestagens or oestrogens from placenta, but did produce small amounts of labelled progesterone and Sa-dihydroprogesterone from fetal gonad. Immunochemical staining of tissues with four antisera specific for enzymes involved in the steroidogenic pathway revealed no staining in sections or placenta but positive labelling for P450 side chain cleavage enzyme (SCC450) and 3~-hydroxysteroid dehydrogenase (3J3-HSD) of the interstitial cells that comprise the bulk of the enlarged fetal gonads during the second half of gestation. Saline extracts of placental tissue showed no activity in three different gonadotrophin assays. In view of this endocrinological in­ activity in the zonary elephant placenta and the probable reliance on maternal luteal sources of progestagens ror maintenance of the pregnant state, the argument is advanced that uncomplicated abortion would probably follow a single administration of a PGF analogue given at any stage of pregnancy. If 50, the treatment might constitute an efficacious method for controlling population increases in elephants maintained in enclosed game parks in Africa.