Melatonin regulates the expression of Bone Morphogenetic Protein 15 (Bmp-15), Growth Differentiation Factor 9 (Gdf-9) and LH receptor (Lhr) genes in developing follicles of rats

This study investigated the effects of melatonin supplementation on the daily mRNA expression of Bmp-15, Gdf-9, FSH (Fshr) and LH (Lhr) receptor genes and the effect of gonadotropin supplementation on protein expression of melatonin-synthetizing enzymes (ASMT and AANAT) during in vitro maturation (IMV) of rat follicle-enclosed oocytes. We also studied the effects of pinealectomy on the mRNA expression of Bmp-15, Gdf-9, Fshr and Lhr genes in immature oocytes and cumulus cells and on the protein expression and immunolocalization of AANAT and ASMT in immature ovaries. Ovaries were collected from sham-pinealectomized (INTACT) and pinealectomized (PINX) females during the light and dark phases of the 12h:12h light-dark cycle. Melatonin increased the Bmp-15 and Gdf-9 mRNA expression in follicle-enclosed oocytes during dark phase and Lhr mRNA expression during the light phase. The daily mRNA expression of Lhr was negatively correlated with the daily mRNA expression of Bmp-15 and Gdf-9 in follicle-enclosed oocytes supplemented with melatonin. There were no phase differences in oocytes mRNA expression of Bmp-15 and Gdf-9 from PINX females. Pinealectomy did not altered the mRNA expression of Lhr gene in cumulus cells. There were no phase differences in ASMT and AANAT expression in ovaries from INTACT and PINX females and their immunolocalization was seen in most of ovarian cells. AANAT expression in follicle-enclosed oocytes supplemented with LH from INTACT and PINX females was greater during the dark phase. The results suggest that melatonin regulates the daily Bmp-15, Gdf-9 and Lhr mRNA expression during the rat follicle development. There is also an indicative that melatonin plays an important role in the relationship between the daily expression of Lhr and the daily expression of Bmp-15 and Gdf-9 in follicle-enclosed oocytes during oocyte maturation process.