Dose response effect of α2-macroglobulin on bovine granulosa cell estradiol production. Granulosa cells from dominant nonovulatory follicles were treated for 18 hours with different amounts of bovine IgG (control), bovine α2-macroglobulin (bα2-m) or human α2-macroglobulin (hα2-m). Bars represent the overall mean ± SEM values for concentrations of estradiol in media after culture of granulosa cells isolated from two follicles (n = 2 cows). Different letters above bars indicate significant (P < 0.01) difference among means. Reproduced from Ireland et al., 2004 .