Progesterone Secretion after LH-Antisera or Ergocryptine Treatment of Normal or Hysterectomized Pseudopregnant Rats1

Rats were treated with LH-antisera (LHAS) or ergocryptine (ECR) on day 8 of pseudopregnancy or day 15 of hysterectomized pseudopregnancy to evaluate the role of LH and prolactin in the luteotrophic process at these times. LHAS reduced progesterone levels in pseudopregnant rats by 24 h after treatment but by 48 h progesterone concentrations had returned to control levels. LHAS extended the length of pseudopregnancy by 5 days; however, progesterone levels were low during this period indicating that luteal activity was not extended and suggesting that LHAS interfered with onset of the next estrous cycle. Progesterone secretion was decreased at 24 and 48 h after LHAS treatment during hysterectomized pseudopregnancy. ECR treatment terminated luteal maintenance in pseudopregnant and hysterectomized pseudopregnant rats resulting in diminished progesterone secretion at 24 and 48 h after treatment and the return of vaginal cycles. Although LHAS or ECR reduced progesterone secretion by 24 h after treatment, in no instance was 20α-dihydroprogesterone (20α-OH-P) secretion elevated at this time. Results of the present studies indicate that LH and prolactin are components of the luteotrophic process on day 8 of pseudopregnancy and day 15 of hysterectomized pseudopregnancy.