Fine Structures of the Oocyte in Relation to Serum, Follicular Fluid Steroid Hormones and IGF-I in the Ovulatory-Sized Follicles in One-Humped Camel (Camelus dromedarius)

BACKGROUND: The following study was carried out to determine the ultrastructural features of the oocyte of the ovulatory-sized follicles in relation to concentrations of steroids and IGF-I in the Follicular Fluid (FF) and serum in the dromedary camel. METHODS: Camel follicles with a clear and healthy appearance were categorized into three classes: follicles 10 to 13.9, 14-17.9 and 18-30 mm diameter. The FF and serum samples were assayed for estradiol-17β, progesterone and IGF-I. Recovered Cumulus-Oocyte Complexes (COCs) were prepared for transmission electron microscopy. RESULTS: The mean (±SD) FF concentrations of progesterone and IGF-I was significantly (p < 0.05) higher in follicles 18 to 30 mm diameter compared to other groups of follicles. There was no difference in the mean (±SD) serum estradiol-17β, progesterone and IGF-I concentrations between camels with different ovulatory-sized follicles (p > 0.05). Oocytes from follicles 18 to 30 mm diameter (group 3) showed more advanced signs of maturation including the disappearance of the nuclear envelope, increased number of microvilli in erect position, the increase in number and size of vesicles and more even distribution of the mitochondria throughout the ooplasm. CONCLUSION: The final stages of oocyte maturation in dromedary camel is associated with increasing progesterone and IGF-I concentrations and constant high estradiol concentration in the follicular fluid which are paralleled with well-defined ultrastructural changes in oocytes.