Abstract
Abstract
Intact and gonadectomized male rats were injected for 4 days with aqueous extracts of midgestation rat placentae to study the effects of this treatment on pituitary secretory function. Experimental rats received daily doses of extract equivalent to one, two, or four placentae; controls were injected with liver extract. At autopsy, 24 hr after the last injection, serum and anterior pituitary glands were collected for radioimmunoassay of FSH, LH, and PRL. Placental extracts caused a dose-related reduction of serum PRL concentration in both intact and gonadectomized rats and depressed circulating LH levels of intact animals. Serum FSH concentration was not affected by this treatment. Pituitary levels of the three hormones were not significantly different between animals injected with placental extract and their liver-injected controls. We conclude that rat placental extract contains a substance, likely to be chorionic mammotropin (rCM), capable of modifying pituitary secretory function during pregnancy.
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