Osmotic stress, plasma renin activity, and spermatogenesis in Vipera aspis

Circulating electrolytes (Na⁺, K⁺), plasma renin-like activity, testosterone, and testis morphology were investigated in early summer during the spermatogenic progressive phase in Vipera aspis subjected to sodium loading and sodium depletion. After sodium loading, plasma sodium and plasma testosterone levels were significantly elevated compared with those of controls, while plasma renin-like activity was depressed, spermiogenesis was increased, the epithelium lining the epididymis was very thick, and the Leydig cells were hypertrophied. After sodium depletion, plasma sodium and plasma testosterone levels were significantly depressed and plasma renin-like activity was significantly elevated. Spermiogenesis seemed to be slightly regressed: the epithelium lining the epididymis was very thin, and the lumen was devoid of spermatozoa. The Leydig cells were hardly visible. All the data strongly suggest that osmotic stress affects gonadal activity in the snake. V. aspis.