Development of Codominant Follicles in Cattle Is Associated with a Follicle-Stimulating Hormone-Dependent Insulin-Like Growth Factor Binding Protein-4 Protease1

• DOI: 10.1095/biolreprod65.1.112
• Publication Date: 2005-10-31T23:33:39Z
• Authors: G.M. Rivera; J.E. Fortune
• Keywords: Follicular fluid

Low molecular weight insulin-like growth factor binding proteins (IGFBPs), particularly IGFBP-4, are believed to inhibit the actions of factors (IGFs). We showed previously that ovarian follicular dominance in cattle is associated with presence a protease degrades IGFBP-4. To test hypothesis specific IGFBP-4 proteolysis selection dominant follicle, we induced codominant follicles (co-DFs) during first wave estrous cycle. The ovaries Holstein heifers were examined twice daily by ultrasonography; when largest follicle reached 6 mm diameter, saline (control, n = 5) or 2 mg recombinant bovine (rb) FSH (FSH, was injected i.m. every 12 h for 48 h. Follicular fluid collected aspiration from two follicles/heifer after last injection. IGFBPs quantified Western ligand blotting/phosphorimaging. activity measured incubating human (rh) substrate, followed blotting/phosphorimaging quantify percent substrate loss and immunoblotting detect proteolytic fragments. Co-DFs did not differ (P > 0.05) single controls size, concentration progesterone level fluid. In contrast, subordinate control smaller, lower higher < 0.05). Concentrations estradiol high follicles, intermediate co-DFs, low co-DFs similar but fourfold than follicles. results strongly suggest an FSH-dependent cattle.