Mononuclear cell-modulation of granulosa cell steroidogenesis in rat: influence of ovarian cycle

The mononuclear cells exert a paracrine influence on the ovarian function, including steroidogenesis. This study examines the ability of the conditioned medium from the cultures of splenic mononuclear cells, obtained during various phases of the ovarian cycle, on progesterone accumulation by the granulosa cells in the culture medium. Female Wistar rats, aged twenty-five days, were made pseudopregnant by an injection of pregnant mare's serum gonadotropin. The splenic mononuclear cells were isolated at follicular phase, early luteal phase, mid luteal phase and late luteal phase and cultured for 48 h. The ammonium sulphate precipitated fraction of the conditioned medium was added to the granulosa cells obtained from immature rats treated with diethylstillboestrol. The granulosa cells were cultured for 48 h, and the progesterone accumulated in the medium was assayed. The conditioned medium from the cultures of the mononuclear cells obtained during follicular phase and late luteal phase inhibited FSH-induced progesterone secretion, whereas conditioned medium obtained from mid luteal phase mononuclear cells enhanced the effect of FSH. The stimulatory effect of db-cAMP on progesterone accumulation in the culture medium is inhibited by conditioned medium obtained from all the phases of the ovarian cycle. This study demonstrates a cyclicity in the behaviour of the splenic mononuclear cells on ovarian steroidogenesis, suggesting a bi-directional paracrine and/or endocrine relationship between ovary and the mononuclear cells.