GONADOTROPHIN RESPONSE AFTER CASTRATION AND SELECTIVE DESTRUCTION OF THE TESTICULAR INTERSTITIUM IN THE NORMAL AND ASPERMATOGENIC RAT

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Abstract
Serum LH [luteinizing hormone] and FSH [follicle stimulating hormone] were measured by radioimmunoassay in adult male rats previously rendered aspermatogenic by a high dose of .alpha.-chlorohydrin. In the aspermatogenic rat serum FSH was elevated but LH levels and androgen dependent organ weights were within normal limits. Transient destruction of the interstitium with a resultant decrease in testicular androgen secretion by ethylenedimethane sulfonate (EDS) in the normal rat preferentially increases serum LH. However, in the aspermatogenic rat EDS increased both serum LH and FSH to levels indistinguishable from those of the normal castrate. The pattern of gonadotropin secretion in the EDS treated aspermatogenic rat suggested that the dynamic changes after the disturbance of the androgenic feedback were faster than those found in the normal male rat. Castration of the aspermatogenic rat produced serum gonadotropin levels comparable to the 27 day normal castrate within 1 and 2 days for LH and FSH, respectively. The data supports the concept of the dual control of pituitary gonadotropin secretions arising from the seminiferous tubule (inhibin) and the interstitium (androgen). The results also suggest that inhibin acts to modify pituitary sensitivity to endogenous LH-RH [releasing hormone] as the removal of the androgenic feedback signal in the aspermatogenic rat either by EDS or castration results in a faster achievement of castrate gonadotropin levels.