FOLLICULAR-FLUID ADMINISTRATION DELAYED, BUT DID NOT PREVENT, THE HEMICASTRATION-INDUCED INCREASE IN FOLLICLE-STIMULATING-HORMONE SECRETIONAND COMPENSATORY TESTICULAR HYPERTROPHY IN RAM LAMBS

To determine whether the post-hemicastration rise in serum FSH is rela ted to compensatory testicular hypertrophy, 4-moold ram lambs were hem icastrated and injected s.c. with 5 ml of saline (HC; n = 5) or steroi d free follicular fluid (HC+FF; n = 5) twice daily for 28 days. Sham-o perated 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 d elayed (p < 0.05) the hemicastration-induced rise in FSH, but only for 14 of the 28 days of treatment; after this time, concentrations incre ased to the levels observed in HC rams. Within 2 days after the last f ollicular fluid injection (Day 30), FSH concentrations increased again to levels greater (p < 0.05) than those observed in HC animals. FSH s ecretion in HC+FF rams then declined to basal values by 7 wk, 2 wk lat er 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 v s. 37.8 +/- 4.7 days, respectively; p > 0.05). Testicular volume, dete rmined 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) b etween INT and HC+FF rams. By the end of the study, a similar degree o f compensatory testicular hypertrophy was observed in HC and HC+FF ani mals. Neither serum LH nor testosterone basal or pulsatile secretion w as affected (p > 0.05) by follicular fluid treatment. In summary, foll icular fluid administration delayed, but did not prevent, the hemicast ration-induced increase in FSH secretion and subsequent compensatory t esticular hypertrophy. The demonstration of a relationship between con centrations of circulating FSH and compensatory hypertrophy suggests t hat this gonadotropin plays a role in mediating the testicular respons e in prepubertal ram lambs.