The Maintenance of Gestation and the Initiation of Lactation in the Mouse in the Absence of Pituitary Prolactin

Summary. Dwarf mice with hereditary prolactin deficiency were rendered fertile by implanting normal mouse pituitary under the kidney capsule. The grafts were removed by unilateral nephrectomy between Days 9 and 16 of pregnancy. All females carried to term and delivered litters. The young died within 2 to 8 days, apparently from lack of milk. The comparison of these results with the effects of hypophysectomy during pregnancy suggests that the mouse placenta produces prolactin-like hormone before it can provide full luteotrophic complex. The involution of mammary glands is slower in dwarfs deprived of the source of prolactin but secreting lh, fsh and acth than in the hypophysectomized animals.