Proteomic analysis of follicular fluid from tropically-adapted goats

The present study was conducted to characterize the major proteome of ovarian follicular fluid from locally-adapted, “Canindé” goats in the northeast of Brazil. Eight estrous cycling goats received a hormonal treatment consisting of medroxyprogesterone acetate, D-cloprostenol and FSH. Fluid was collected by laparoscopy from small (<3 mm), medium (3-4 mm) and large (>4 mm) follicles and then, proteins were analyzed by 2-D SDS-PAGE and tandem mass spectrometry. Thirty-six proteins were identified in the goat follicular fluid, including albumin, immunoglobulins, ceruloplasmin, complement factor B, alpha-1B-glycoprotein precursor, serotransferrin, complement C3 and serpins, among others. Albumin and immunoglobulins were the most abundant proteins. Protein concentrations were similar in the fluid from small (45.3 ± 3.1 mg/mL), medium (44.2 ± 3.3 mg/mL) and large follicles (45.1 ± 2.3 mg/mL). The intensities of spots identified in 2-D gels as serotransferrin, zinc-alpha-2-glycoprotein-like, complement factor B and complement protein C3 differed (P < 0.05) among follicle categories. The amount of serotransferrin was greater in the medium than small follicles (P < 0.05). Content of zinc-alpha-2-glycoprotein-like, complement factor B and complement C3 was greater (P < 0.05) in the fluid of large follicles than in medium follicles. Based on gene ontology, the major molecular functions associated with goat follicular fluid proteins were binding and catalytic activity, while the main biological processes were related to regulation, cellular processing, location and the immune system. In conclusion, the major proteome of the follicular fluid from goats subjected to hormonal stimulation was elucidated in the present study. Also, molecules associated with follicle development are potential biomarkers of oocyte competence were prevalent.