The regulation of kit ligand expression in rat granulosa cells by ovarian factors

Abstract

The aim of this research was to clarify the actions and interactions between factors implicated in the regulation of kit ligand (KITL) expression in rat granulosa cells by measuring Kitl1 and Kitl2 mRNA levels through quantitative PCR. Our findings included the observation that induction of the transcripts in primary granulosa cells by follicle-stimulating hormone (FSH), was not mimicked by dibutyryl cAMP and forskolin in spontaneously immortalized granulosa cells (SIGC). Transforming growth factor-beta1 (TGF-beta1) suppressed Kitl1 and Kitl2 mRNA levels in primary granulosa cells and SIGC - an effect mediated via Smad2 and Smad3. Exposure of primary granulosa cells to estrogen in vivo, via diethylstilbestrol (DES)-priming of immature rats and in vitro, by culturing in the presence of 17beta-estradiol, inhibited Kitl1 and Kitl2 mRNA expression, an effect mediated via TGF-beta1. Therefore, three levels of control are involved in regulating Kitl mRNA expression in the ovary: gonadotropins, local ovarian factors and steroid hormones.