Effect of ACTH and hCG on the Expression of Gonadotropin-Inducible Ovarian Transcription Factor 1 (Giot1) Gene in the Rat Adrenal Gland

Abstract

Gonadotropin-inducible ovarian transcription factor-1 (Giot1) belongs to a family of fast-responsive genes, and gonadotropins rapidly induce its expression in steroidogenic cells of ovaries and testes of rats. Gonadal Giot1 gene expression is regulated by cyclic adenosine monophosphate (cAMP) -dependent protein kinase A pathway, with essential role of orphan nuclear receptor NR4A1 transcription factor (nuclear receptor subfamily 4, group A, member 1). A recent study reports that Giot1 is also expressed in adrenals, however, the mechanism of its regulation in adrenal gland is yet to be identified. Therefore, the aim of this study was to characterise the changes in Giot1 gene expression in male and female rat adrenals using wide range of in vivo and in vitro experimental models. Special emphasis was directed at the Giot1 gene regulation by ACTH and gonadotropin. In our study, we found that ACTH rapidly stimulates Giot1 expression both in vivo and in vitro. However, gonadotropin does not affect the adrenal Giot1 gene expression, presumably due to the low expression of gonadotropin receptor in adrenals. Both testosterone and estradiol administered in vivo had inhibitory effect on Giot1 gene expression in the adrenals of post-gonadectomized adult rats. Further, our studies revealed that the intracellular mechanism of Giot1 gene regulation in rat adrenals is similar to that of gonads. As in the case of gonads, the expression of Giot1 in adrenal gland is regulated by cAMP-dependent signaling pathway with essential role of the NR4A1 transcription factor. The results of our studies suggest that Giot1 may be involved in the regulation of rat adrenocortical steroidogenesis.