[Testicular androgens and spermatogenetic cycles in the viviparous lizard].

Androstenedione, testosterone and dihydrotestosterone levels were measured in the testis of 36 males of the viviparous lizard throughout a period (from end of May to end of July) characterized by the transition between two spermatogenetic cycles and by very low levels of plasma testosterone. The sudden rise of testicular testosterone and androstenedione in June is concomitant with a degeneration of the seminiferous epithelium. It coincides with a transient appearance of testicular dihydrotestosterone. During the next decline in the levels of testosterone and androstenedione, it occurs a restoration of the seminiferous tubules which resume spermatogenesis (proliferation of spermatogenia and prophase of first meiotic division). The part played by some testicular steroids in the control of spermatogenesis is discussed.