We investigated the expression of calcium-dependent phospholipid binding protein annexin-II (Ann-II) messenger RNA (mRNA) during preantral follicle development and in oocytes from antral follicles of different diameters (< 3 mm, 5 to 8 mm and > 8 mm). The action of retinol on Ann-II mRNA expression in mature oocytes was also examined. Only oocytes from secondary preantral follicles expressed Ann-II mRNA and at the germinal vesicle stage expression by oocytes from follicles larger than 8 mm was significantly higher (p < 0.05) compared with oocytes from follicles smaller than 3 mm or between 5 and 8 mm. Ann-II mRNA expression by metaphase II oocytes from follicles larger than 8 mm was significantly higher (p < 0.05) than that from oocytes from follicles smaller than 3 mm, with oocytes from both these size-classes showing similar levels of Ann-II mRNA expression as oocytes recovered from 5-8 mm follicles. In the presence of retinol, Ann-II mRNA expression was higher than when retinol was absent (p < 0.05). Our data indicate that Ann-II mRNA expression is highest in competent oocytes and that retinol increases Ann-II mRNA and may be involved in the regulation of oocyte competence by decreasing the translation and/or degradation of Ann-II mRNA.
bovine oocytes; annexin II; retinol
