Abstract
The role of prolactin (PRL) in the maintenance of the corpus luteum (CL) of pregnancy in adult female ferrets was investigated. Twelve animals were hypophysectomized on Day 5 or 6 of gestation (Day 0 = mating). Eight received 250 µg bovine PRL/day and the remaining 4 received no further treatment. A third group of 4 ferrets was subjected to sham hypophysectomy. Laparotomy was performed on Day 15 and hypophysectomized ferrets were autopsied on Day 20. No embryos implanted in the hypophysectomized untreated ferrets and serum progesterone levels at Days 15 and 20 were less than in either sham hypophysectomized or hypophysectomized PRL treated ferrets (P<0.05). Implanted embryos were observed in all sham treated females, in 4 of the PRL treated females at Day 15 and in 5 PRL treated females on Day 20. Uterine morphology in PRL treated females that failed to contain implanted embryos could be likened to that seen in pseudopregnant ferrets. Serum progesterone levels were not different between sham treated and hypophysectomized PRL treated females at Day 15 or 20. Both groups had significantly higher progesterone concentrations when compared with hypophysectomized, untreated ferrets (P<0.05). It is concluded that PRL can sustain luteal progesterone production during the first half of pregnancy in hypophysectomized ferrets. Further, PRL can qualitatively maintain the CL of pregnancy as evidenced by its ability to induce embryo implantation in hypophysectomized ferrets.

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