Follicular fluid administration delayed, but did not prevent, the hemicastration-induced increase in follicle-stimulating hormone secretion and compensatory testicular hypertrophy in ram lambs

Abstract

To determine whether the post-hemicastration rise in serum FSH is related to compensatory testicular hypertrophy, 4-mo-old ram lambs were hemicastrated and injected s.c. with 5 ml of saline (HC; n = 5) or steroid-free follicular fluid (HC+FF; n = 5) twice daily for 28 days. Sham-operated intact lambs, injected with saline, served as controls (INT; n = 5). Blood samples were collected frequently during the first 48 h, daily for the remainder of the first week, and then three times/wk for the next 11 wk. Serum FSH concentrations in HC lambs increased above presurgery levels by 9 h, peaked at 13 days, and returned to baseline as compared to INT controls by 5 wk. Follicular fluid administration delayed (p < 0.05) the hemicastration- induced rise in FSH, but only for 14 of the 28 days of treatment; after this time, concentrations increased to the levels observed in HC rams. Within 2 days after the last follicular fluid injection (Day 30), FSH concentrations increased again to levels greater (p < 0.05) than those observed in HC animals. FSH secretion in HC+FF rams then declined to basal values by 7 wk, 2 wk later than in HC rams. Although the time course differed, the duration of elevated FSH did not differ between HC and HC+FF rams (36.4 ± 2.0 vs. 37.8 ± 4.7 days, respectively; p > 0.05). Testicular volume, determined on the last day of treatment (Day 28), was 70% greater (p < 0.05) in HC than in INT or HC+FF lambs; volume did not differ (p > 0.05) between INT and HC+FF rams. By the end of the study, a similar degree of compensatory testicular hypertrophy was observed in HC and HC+FF animals. Neither serum LH nor testosterone basal or pulsatile secretion was affected (p > 0.05) by follicular fluid treatment. In summary, follicular fluid administration delayed, but did not prevent, the hemicastration-induced increase in FSH secretion and subsequent compensatory testicular hypertrophy. The demonstration of a relationship between concentrations of circulating FSH and compensatory hypertrophy suggests that this gonadotropin plays a role in mediating the testicular response in prepubertal ram lambs.