CONTROL OF LUTEAL FUNCTION IN THE MINK (MUSTELA-VISON)

The ranch mink was studied to determine the role of pituitary luteotro phins on corpus luteum (CL) function before and after implantation. Tw elve mink were treated with monoclonal antiserum against gonadotrophin -releasing hormone (GnRH), and 12 with an irrelevant monoclonal antibo dy during embryonic diapause. Activation of the CL, plasma progesteron e concentration and embryo implantation were unaffected by this treatm ent. In a second trial, groups of ten mink were treated with GnRH anti bodies, bromocriptine, bromocriptine plus 0.5 mg prolactin per day per animal, or ethanol vehicle. Comparison of the consequent profiles of progesterone indicated that both bromocriptine and anti-GnRH compromis ed postimplantation CL function by inducing regression of the corpus l uteum. Incubation of dissociated luteal cells from ovaries of mink at 21-24 days after implantation with either LH or prolactin increased th e accumulation of progesterone over 2 h. Addition of 25-hydroxy-choles terol (25OHC) as substrate increased basal levels and the progesterone accumulation stimulated by LH and prolactin; the increases induced by luteotrophins were additive. There was an apparent synergistic intera ction between prolactin and canine low-density lipoproteins (LDL) in t he stimulation of progesterone secretion in vitro. The results are int erpreted to indicate that LH/FSH are not required for luteal support d uring embryonic diapause, or for luteal activation. Prolactin is neces sary for luteal activation, and LH and/or FSH and prolactin are obliga te luteotrophins during the postimplantation period in the mink.