Expression of melanocortin receptors mRNA, and direct effects of ACTH on steroid secretion in the bovine ovary.
Melanocortin receptors (MCRs) are involved in physiological responses to ACTH, as well as to α-, β- and γ-melanocyte-stimulating hormone (α-, β- and γ-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.
Department of Morphological Sciences, Faculty of Veterinary Sciences, National University of Litoral, Santa Fe, Argentina.
A N
AN
Amweg
A
A
Paredes
N R
NR
Salvetti
H E
HE
Lara
H H
HH
Ortega
D000324:Adrenocorticotropic Hormone / Q000494:pharmacology*; D000818:Animals; D002417:Cattle / Q000378:metabolism*; D004958:Estradiol / Q000378:metabolism*; D005260:Female; D006854:Hydrocortisone / Q000378:metabolism*; D006080:Ovarian Follicle / Q000187:drug effects / Q000378:metabolism; D010053:Ovary / Q000187:drug effects / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism*; D044101:Receptors, Melanocortin / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013799:Theca Cells / Q000187:drug effects / Q000378:metabolism
D012333:RNA, Messenger; D044101:Receptors, Melanocortin; D004958:Estradiol; D000324:Adrenocorticotropic Hormone; D006854:Hydrocortisone