The growth and atresia of individual antral bovine follicles have been monitored using sequential ultrasonography, and it has been established that growth of follicles > 4 mm takes place in 2 or 3 waves during the estrous cycle. Emergence of successive follicular waves during the estrous cycle was associated with increases in circulating concentrations of FSH that preceded wave emergence by 1 day. During an anovulatory wave, the development of each follicle has been subdivided into growing (increasing diameter), static (no change in diameter), and regressing (decreasing diameter) phases. These ultrason-ically classified phases have been shown to be closely correlated with the follicle’s ability to produce steroid and protein hormones (estrogen:progesterone and estradiol:an-drostenedione ratios, a-inhibin and dimeric inhibin concentrations) indicative of follicle health or atresia. The dynamics of follistatin expression in bovine follicles and corpora lutea relative to follicular wave status and the stage of the estrous cycle have apparently not been documented. buy birth control online
The present study was designed to characterize the relative amount and distribution of follistatin in dominant and subordinate follicles during the growing, static, and regressing phases; to compare the features of follicles of the anovulatory versus ovulatory waves; and to characterize the changes in follistatin distribution during the immature, mature, and postmature phases of the corpus luteum in cattle.