Apoptotic Cells in Dominant Follicles in Japanese Black Cows

Abstract

Ovarian dynamics in six Japanese Black cows with two and three follicular waves (FW s) were determined by means of ultrasonography twice daily and blood was sampled for progesterone analysis. Ovariectomy was performed at Day 18 a.m. (Day 0 = estrus) to evaluate the apoptotic cells in the preovulatory dominant follicle (DF) by TUNEL method. Three cows showed 2 follicular waves (FWs) in the estrous cycle, where emergence of FW 1 and 2 were observed on Day 1.3±0.3 and 10.2±0.3, respectively. Maximum diameter of the DF in FW 1 was 12.2±O.8 mm on Day 7 p.m. and 11.7±0.8 mm on the day of ovariectomy in FW 2. The other three cows have 3 FWs where FW 1, 2 and 3 emerged on Day 1.2±0.3, 8.8±0.3 and 14.8± 1.3, respectively. The DF of FW 1, 2 and 3 increased its diameter until Day 7 a.m. (12.6 ± 0.8 mm) and Day 15 p.m. (11.2 ± 1.3 mm), and the day of ovariectomy (9.4±3.0 mm), respectively. The prevalence of apoptotic cells in GCs and TCs in the preovulatory DF was ~.7±2.3%, 2.8±0.6% in cows with 2 FWs and 10.5±2.5%, 5.8±3.0% in cows with 3 FW s, respectively. The prevalence of apoptotic cells was significantly higher for GCs than TCs in all groups (P<0.05). In conclusion, the results showed that apoptotic cells occurred in preovulatory DF on Day 18 of the estrous cycle and the prevalence of apoptotic cells was higher in GCs than in TCs. Key words: apoptosis, Japanese Black cows, ovariectomy, preovulatory dominant follicle, ultrasonography