Abstract
Summary
The results of the experiments reported herein support the findings of Malven and Sawyer (11) that a luteotropic hormone, capable of stimulating luteal cell synthesis and secretion of progestogen, can also be luteolytic. Rat chorionic mammotropin, a potent luteotropic hormone detectable during midpregnancy may under some circumstances have an opposite effect on luteal cells and become luteolytic. The dose of 0.1 ml of serum from rats 12 days pregnant promoted hypertrophy in newly formed luteal cells and continuing progestogen secretion if injected commencing on the day of hypophysectomy or 1 day later. This luteotropic potency is equal to about 1.5 IU of ovine pituitary LTH as tested in 1-month-old rats. Both luteotropic hormones induce luteolysis at the same dose level (or higher levels) if the luteal cells are deprived of trophic hormone for 48 hr or more. There has been no evidence favoring a rat placental ICSH (LH) as the luteolytic factor in these experiments but this possibility, under different circumstances, is not excluded.
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