Relationship between the decidual response and ovarian steroidogenesis in the unilaterally ovariectomized pseudopregnant rat.

Abstract

The influence of the decidual cell reaction (DCR) on luteal and non-luteal ovarian steroidogenesis was ascertained on day 8 of pseudopregnancy in unilaterally ovariectomized rats. Whether a 'local' interaction existed between the DCR and ovarian steroidogenesis was of particular interest. Holtzman rats were subjected to unilateral ovariectomy and after exhibiting two successive oestrous cycles, they were rendered pseudopregnant by cervical stimulation at oestrus (day 1). On day 5 of pseudopregnancy, rats were subjected to a unilateral stimulus to induce a decidual cell reaction (ipsilateral or contralateral to the remaining ovary) or to sham-operation. On day 8 of pseudopregnancy, they were killed by decapitation and serum was stored for radioimmunoassay of progesterone, androgen, oestradiol, prolactin, FSH and LH. Also the corpora lutea and non-luteal portion of the ovary (NLO) were incubated for 2 h in Krebs–Ringer bicarbonate buffer. Steroid concentrations were determined in the corpora lutea and NLO before and after incubation and in the incubation media. No differences were observed between groups (no DCR, ipsilateral DCR, contralateral DCR) in the serum concentrations of progesterone, androgen, FSH, LH or prolactin. However, serum levels of oestradiol were significantly lower than those levels in rats lacking DCR. No 'local' steroidogenic effect of the DCR was observed in the corpora lutea or NLO; although it appeared that the DCR could stimulate luteal progesterone production since corpora lutea from rats with ipsilateral DCR produced more progesterone in vitro than rats lacking DCR (but not than rats with contralateral DCR). The presence of a DCR was associated with lower levels of oestradiol in serum, corpora lutea and NLO and also with lower in-vitro production of oestradiol by NLO and corpora lutea than unilaterally ovariectomized rats lacking DCR. Since androgen levels in serum, corpora lutea and NLO were not altered by the presence of a DCR, it seems plausible that the DCR may alter oestrogen synthesis (aromatase) in the ovary.