Cortisol affects testicular development in male common carp, Cyprinus carpio L., but not via an effect on LH secretion

Previous work showed that prolonged elevated cortisol levels, implicated in the stress adaptation, inhibits testicular pubertal development in male co mmon carp, as well as an impairment of the synthesis of the 11-oxygenated a ndrogens. This may be a direct effect of cortisol on the testis or via the gonadotropin secretion by the pituitary. The aim of the present study was t o investigate whether cortisol has an effect on pituitary LH secretion. Juv enile common carp were fed with cortisol containing food pellets. Elevated cortisol levels blocked the increase in testosterone levels and pituitary L H content, but induced higher plasma LH levels at the end of puberty. The i n vitro LH release capacity was correlated to the pituitary LH content. At the final stage of pubertal development, when a significant difference in p ituitary LH content was observed, sGnRHa-induced LH release was also decrea sed. Testosterone has been shown to induce development of pituitary gonadot rophs, leading to an increase in LH content and GnRH-inducible LH release, but a decrease in plasma LH levels. We observed decreased plasma testostero ne levels as a consequence of prolonged cortisol treatment. It is hypothesi sed that cortisol inhibits the testicular testosterone secretion and thereb y, prevents LH storage. In vitro, this leads to a reduced GnRH-inducible LH release, but in vivo to increased LH plasma levels. It is very unlikely th at the impaired testicular development is due to an effect of cortisol on L H secretion. (C) 2001 Elsevier Science Inc. All rights reserved.