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L García1 , P Rosas1 , R Domínguez1 *
Biology of Reproduction Research Unit, FES-Zaragoza, UNAM, México DF, México 1
Thymectomy performed on 10-day-old mice delays puberty and decreases follicular population (Biol Reprod 52, Supp 1:296). In prepubertal mice, thymulin stimulates gonadotropin (GnRH)-induced ovulation (Biol Reprod 54, Supp 1:115). We studied the ovulatory response to GnRH administration in 10-day thymectomized mice (Tx-10) and the effects of thymulin treatment prior to GnRH injection. Beginning on day 10 of age, groups of Tx-10 and control mice were treated daily with thymulin (12 ng/g bw) or saline. On day 25 the animals were injected with 1 IU of eCG, 54 h later with 3 IU of hCG and killed 20 h later. The ovulation rate was similar in control and Tx-10 mice treated with GnRH. The number of ova shed (7.6±0.8 vs 13.4±1.3, P<0.05) and the uterine weight (50.0±2.9 vs 95.5±11.7, P<0.05) were significantly lower in Tx-10-GnRH-treated mice. In control animals thymulin injection did not modify GnRH-induced ovulation, while in Tx-10 mice, thymulin treatment provoked a significant increase in the number of ova shed (11.8±0.6 vs 7.6±0.8, P<0.05) and uterine weight (84.9±4.6 vs 50.0±2.9 mg, P<0.05). Estradiol (7.2±1.5 vs 33.6±8.8, pg/ml, P<0.05) and progesterone (5.6±1.0 vs 9.0±0.6 ng/ml, P<0.05) serum levels were significantly lower in Tx-10 animals. Thymulin administration prior to GnRH injection to normal animals resulted in a decrease in estradiol and progesterone serum levels (8.4±2.0 vs 33.6±8.8; 6.1±0.7 vs 9.0±0.6, P<0.05). In Tx-10 thymulin-GnRH-treated animals, estradiol levels increased (14.0±2.7 vs 7.2±1.5, P<0.05). Present results suggest that thymulin is responsible for the low ovulatory response to exogenous GnRH in Tx-10 mice. Thymulin also seems to play a role in the regulation of steroid hormone release. Supported by DGAPA IN225598.
This abstract is being presented on Tuesday, August 3 at 8:00 AM to 10:15 AM at CUB 2nd Floor Ballroom.