| dc.description.abstract | Melanocortin receptors (MCRs) are involved in physiological responses to ACTH, as well as to -, - and -melanocytestimulating
hormone ( -, - and -MSH). Their expression has previously been analyzed in various bovine tissues; however, there
are apparently no reports regarding their localization in the ovaries. In the present study, the expression of MCR mRNA in various
bovine ovarian structures was characterized with reverse transcription polymerase chain reaction (RT-PCR). Furthermore, whether
ACTH affected follicular components by affecting steroid secretion in fragments of ovarian follicular wall of medium and large
antral follicles cultured in serum free medium with 1, 10, and 100 nM ACTH, was also determined. Melanocortin receptors
mRNA was localized in the theca cells of various follicular stages, whereas only MC3R mRNA was weakly evident in granulosa
cells. Melanocortin receptors 1, 2, and 3 mRNA were present in the CL, whereas in stroma, only MC2R mRNA was expressed.
There were significant increases in estradiol and cortisol concentrations in response to ACTH in medium follicles, as well as
increased concentrations of testosterone and cortisol in large follicles. These results confirmed earlier reports in other species, and
demonstrated that MCRs were present in bovine ovaries. Since ACTH induced steroid secretion from the ovary in vitro, we
inferred that melanocortin peptides could be involved in regulatory mechanisms related to ovarian functions, e.g. ovulation,
steroidogenesis, and luteal function. | |
