Effect of Differing Degrees of Destruction of the Rat Seminiferous Epithelium on Levels of Serum Follicle Stimulating Hormone and Androgen Binding Protein1

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Abstract
The effect of differing degrees of destruction of the seminiferous epithelium on serum FSH [follicle stimulating hormone] levels and on Sertoli cell secretory function was studied in adult male rats. Germinal cell aplasia (Sertoli cell-only syndrome, SCO) was induced in male rats by fetal irradiation (250 rads) on day 20 of gestation. Destruction of the seminiferous epithelium was induced by treatment with hydroxyurea (HU) or chornic feeding of a vitamin A-defifient diet (VAD). Serum FSH, LH [luteinizing hormone] and testosterone were measured to assess pituitary-testicular interaction, and testicular androgen binding protein (ABP) was measured to evaluate Sertoli cell secretory function in these states. Serum LH was significantly elevated in all 3 treatment groups, whole serum testosterone was significantly lower than normal only in SCO rats. Elevation of LH and lowered testosterone levels suggest that there is partial Leydig cell failure in rats with germinal cell aplasia induced by fetal irradiation. Significantly elevated levels of serum FSH were seen in all 3 treatment groups; degree of elevation was proportional to severity of the induced testicular damage (normal adult males 378 .+-. 27, HU treated 751 .+-. 28, VAD 1019 .+-. 49 and SCO rats 1070 .+-. 54 ng/ml, mean .+-. SEM [standard error of the mean]). Both the secretion rate of ABP as measured by its accumulation in the testis in the 16 h following efferent duct ligation, and the total amount of ABP in testis and caput epidiymis were decreased in all 3 treatment groups in proportion to severity of induced testicular damage. Sertoli cell secretory function was impaired as a result of treatments used to induce testicular damage. Impaired Sertoli cell secretory function in association with elevated serum FSH suggests that feedback regulation of FSH may be a function of the Sertoli cell.