Pituitary Hormone Control of Implantation in the Mouse

Abstract

In hypophysectomized pregnant mice replacement therapy designed to mimic the normal physiological situation showed that FSH in combination with either prolactin or LH, or prolactin plus LH, could initiate implantation in the absence of the pituitary gland. No pituitary hormone was by itself capable of achieving this result. The combination of prolactin with FSH gave better results than a combination of LH with FSH. Prolactin from sheep, cattle or rats was equally effective in combination with ratFSH in initiating implantation. In mice exhibiting suckling-induced delay of implantation this delay was terminated by injection of FSH. GH by itself or in conjunction with other hormones had no significant effect on implantation or on any of the other parameters associated with implantation that were measured.On the basis of these experimental results it is suggested that" prolactin and LH are involved with progesterone production and FSH with oestrogen production, both of which are required for implantation in the mouse.

Hypothalamic Control of Prolactin Secretion, and the Multiple Reproductive Functions of Prolactin

“…714 In humans, this function has served as a critical regulator of population growth, spacing the timing of births to allow the mother to ration her metabolic investment in reproduction across sequential pregnancies. 717,718 Despite the extensive impact on mammalian reproductive physiology, our understanding of the mechanisms mediating lactational infertility remains incomplete. 716 Even here, a delayed implantation ensures that the new litter is not born until the appropriate time of weaning of the original pups.…”