Luteal Control of Nidation in the Ferret (Mustela putorius)1

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Abstract
The role of corpora lutea in initiating nidation in ferrets [M. putorius] using the techniques of follicular autotransplantation and exogenous administration of progesterone were studied. Blood samples were obtained at regular intervals between day 6 and 20 (coitus = day 0) and the plasma assayed for progesterone by radioimmunoassay. Progesterone capsules, inserted under the skin immediately following ovariectomy on day 6, failed to offset withdrawal of ovarian hormones as 0/7 ferrets had implanted blastocysts. Progesterone capsules inserted following ovariectomy on day 8 were, successful in initiating nidation at the normal time in 100% of the animals (6/6). When mature follicles were autotransplanted to the kidney capsule on day 1, followed by ovariectomy on day 6, nidation occurred in 1/7 animals by day 20. Follicular transplantation followed by ovariectomy on day 8 resulted in nidation in 1/5 animals, though a delay of implantation lasting several days occurred. Nidation occurred in 4/6 animals after a short period of delay, when progesterone was administered following autotransplantation of follicles on day 1 and ovariectomy was performed on day 6. Viability of implanted embryos was demonstrated by visualization of embryonic heart beat. Administration of progesterone alone on day 6 was not sufficient to induce nidation and ectopic corpora lutea were secreting another hormone(s) prior to day 8, which acted in conjunction with progesterone to induce nidation. Ferret blastocysts can withstand a 7 day period of experimentally induced delay of implantation without loss of viability.