GONADOTROPHIC EFFECTS OF EXOGENOUS SEX HORMONES ON THE TESTES OF SPARROWS1

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Abstract
Injn. of 0.25 mg. of testosterone propionate daily will stimulate complete spermatogenesis in the sparrow, provided the testis has attained the stage of development (2.0-3i0 mm. in greatest diam.) at which androgen begins to be produced in readily measurable amts., and will maintain complete spermatogenesis for at least 80 days. Estrogen has no stimulating effect on the testis at any stage of development. Both estrogen and androgen suppress the hypophysis of the sparrow. At any time that the hypophysis is not releasing gonadotrophic hormones in amts. sufficient to have a stimulating effect on the testis, the testis can be brought to the stage at which androgen is produced by the injn. of pregnant mare serum, after which the substitution of androgen for the PMS will bring about complete spermatogenesis. It is therefore concluded that gonadotrophic hormones are essential for bringing the sparrow''s testes up to the stage at which androgen is produced in measurable amts., but that after this stage is reached androgen alone is sufficient to carry spermatogenesis to completion. Injected andrbgen does not produce any visible suppression of the interstitial tissue. Therefore, it is difficult to determine both the source of the androgen in the normal testis and the way in which exogenous androgen acts to bring about complete spermatogenesis.