AbstractThe effects of vertebrate gonadotropin‐releasing hormone (GnRH) variants on plasma and testicular androgen level in intact and hypophysectomized (PDX) male frogs,Rana esculenta, have been investigated. In intact animals, mammalian (m)‐GnRH, m‐GnRH analog (buserelin), salmon (s)‐GnRH, chicken (c) I‐GnRH, cII‐GnRH, D‐Arg6‐cII‐GnRH (cII‐GnRHA), and lamprey (l)‐GnRH (1.5μg and 6μg, total dose given on alternate days for 5 days) were able to enhance androgen production showing that specificity of pituitary responsiveness to GnRH variants appears to be low. Chicken II‐GnRH was more effective than s‐GnRH in eliciting testicular and circulatory androgen level increase. Moreover, in animals treated with 6μg of cII‐GnRH and s‐GnRH in combination, androgens decreased as compared with animal treated with cII‐GnRH only, suggesting that GnRH receptors bind preferentially the s‐GnRH form. In PDX animals, buserelin (1.5 and 6μg), cII‐GnRH, and its analog (6μg) were able to increase plasma androgen levels whereas testis androgen concentrations were increased by cII‐GnRH (1.5 and 6μg), D‐Arg6‐cII‐GnRHA, and buserelin (6μg). Since androgen production in PDX animals is influenced especially by peptides sharing cII‐GnRH structure, it is suggested that a testicular cII‐GnRH‐like material play a role as