Blood pregesterone levels in pseudopregnant rats: effects of partial removal of luteal tissue.

Abstract

Progesterone levels in peripheral blood were measured throughout the pseudopregnancy period by a competitive protein-binding technique in individual female (R × U) F1 hybrid rats. Rats made pseudopregnant by sterile copulation or electrical stimulation of the uterine cervix showed similar changes in progesterone levels during pseudopregnancy. Blood progesterone levels increased gradually from 3 µg/100 ml on day 0 (=day of vaginal cornification) until a plateau of 10 µg/100 ml was reached on day 5 of pseudopregnancy. After day 8 a very gradual decreased was observed which resulted in a level of about 2 µg/100 ml on days 14–15. In order to investigate a possible compensatory reaction of corpora lutea (CL) during pseudopregnancy progesterone levels were measured after unilateral ovariectomy (ULO) at various days of pseudopregnancy and after cauterization of CL on days 1 and 2 of pseudopregnancy. After ULO on day 0 the maximal progesterone levels remained low (5 µg/100 ml vs 9 µg/100 ml in sham-operated anima...