Fibronectin concentrations correlate with ovarian follicular size and estradiol values in equine follicular fluid

The amounts of total protein, albumin, fibronectin, α 2-macroglobulin (α 2-M), immunoglobulin G, ceruloplasmin and antithrombin were determined in fluids collected from 53 preovulatory equine follicles and compared with the contents of estradiol-17β, progesterone and androstenedione, with follicle size and the amounts of the equivalent proteins in normal equine plasma. The concentration of fibronectin and the fibronectin/albumin ratios increased significantly with follicle size and with follicular estradiol levels. The α 2-M levels and α 2-M/albumin ratios correlated with follicle size but not with hormone content. Both fibronectin and α 2-M were present in lower amounts in follicular fluid compared with plasma while the other proteins were present in similar amounts. Among the proteins evaluated, there was a positive correlation between the amount of the protein in the follicular fluid and the molecular weight of the protein.