Progesterone, 20alpha-dihydroprogesterone and PGF; interrelated hormonal changes during pseudo-pregnancy in the rat

Ovarian and uterine tissue concentrations of progesterone, 20alpha-dihydroprogesterone (20alphaOHP) and prostaglandin F (PGF) were measured during hormonally-induced pseudopregnancy, as were plasma levels of progesterone and 20alphaOHP, in hysterectomised and sham-operated rats. Elevated levels of PGF in uterine and ovarian tissues were coincident with declining concentrations of progesterone and increasing concentrations of 20alphaOHP in the sham-operated rats. Maximum PGF concentrations were apparent in uterine tissue 14 days after hCG injection, coincident with the plasma, ovarian and uterine nadir concentrations of progesterone. A small but statistically significant increase in ovarian PGF was apparent at this time in sham-operated rats. This elevation of ovarian PGF was abolished by hysterectomy.