S. Day, L. Birnbaumer
The effect of administering a luteolytic dose of hCG (100 IU, iv) to 9-day pseudopregnant rabbits that received either no other treatment (controls) or one of two estradiol (E-1.5 or E-15) treatments was studied. E-1.5 and E-15 consisted of 1.5 μg estradiol (E) every 12 h and 15 μg E every 12 h, respectively; these treatments were administered sc in sesame seed oil starting at 2200 h on day 8 and continued through 2200 h on day 11. Animals were bled daily from days 9–12 and sacrificed between 1000–1100 h on day 12, at which time serum and corpora lutea (CL) progesterone content, weight, and adenylyl cyclase activities stimulated by LH (10 μg/ml) and isoproterenol (Iso; 10−4m) were determined. We found that 1) neither low (E-1.5) nor high (E-15) E treatment prevented functional luteolysis (drop in serum progesterone) induced by hCG; 2) E-15 but not E-1.5 prevented structural luteolysis (CL weight loss) induced by hCG; 3) E-15 but not E-1.5 resulted in CL progesterone levels that, after hCG, were indistingu...