Oxytocin,prostaglandins E and F,estradiol, progesterone,sodium, and potassium in preovulatory bovine follicles either developed normally or stimulated by follicle stimulating hormone

To determine the differences between stimulation by follicle stimulating hormone (FSH) and normal development of follicles in heifers and the endocrinologic events associated with ovulatory development of follicles in heifers, follicular fluid was aspirated from follicles (n = 627) at 24, 48, and 72 h after estrus synchronization (via prostaglandin F_2α (PGF_2α)) from control animals (n = 10/time period) and a treatment group (n = 10/time period) that received FSH. No endocrinologic or ionic differences were noted between follicles harvested from control or FSH-stimulated animals within follicular size or time (24, 48, or 72 h). No interaction of treatment (FSH stimulation vs controls) by time was detected; thus the effect and timing of the LH surge was similar between treatments.At 48 h after PGF_2α administration, sodium from follicular fluid decreased and potassium increased, signifying a considerable physiologic change in the follicle. Follicular prostaglandins E and F increased ten-fold by 72 h, and these changes were primarily found in the estrogen-inactive follicles at 72 h. Though progesterone concentrations within follicular fluid tended to increase throughout the three periods and increased with enlargement of follicular size, a major increase was detected 72 h after PGF_2α injection. Estradiol concentrations tended to increase with enlargement of follicular size within a time period, but estradiol concentrations in the follicles greater than 10 mm in diameter decreased with time (24, 48, and 72 h) after PGF_2α. Concentrations of oxytocin increased with increases in follicular diameter, and the time trends were similar to changes in follicular progesterone. By 72 h after PGF_2α administration, follicular estradiol) was decreasing in concentration and progesterone and oxytocin were increasing, thus signifying a change in the secretory role of the granulosa cells.