Effects of gonadotropin-releasing hormone variants on plasma and testicular androgen levels in intact and hypophysectomized male frogs, Rana esculenta.
The 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 (1.5 micrograms and 6 micrograms, 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 6 micrograms 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 6 micrograms), cII-GnRH, and its analog (6 micrograms) were able to increase plasma androgen levels whereas testis androgen concentrations were increased by cII-GnRH (1.5 and 6 micrograms), D-Arg6-cII-GnRHA, and buserelin (6 micrograms). 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 local modulator of the gonadal activity in Rana esculenta.
D'Antonio
M
M
Dipartimento di Fisiologia Umana e Funzioni Biologiche Integrate Filippo Bottazzi, I Facoltà di Medicina e Chirurgia, Naples, Italy.
Fasano
S
S
de Leeuw
R
R
Pierantoni
R
R
D000595:Amino Acid Sequence; D000704:Analysis of Variance; D000728:Androgens / Q000097:blood* / Q000378:metabolism; D000818:Animals; D007987:Gonadotropin-Releasing Hormone / Q000031:analogs & derivatives / Q000737:chemistry / Q000494:pharmacology*; D007016:Hypophysectomy; D008297:Male; D008969:Molecular Sequence Data; D011893:Rana esculenta; D013329:Structure-Activity Relationship; D013737:Testis / Q000187:drug effects / Q000378:metabolism*
D000728:Androgens; D007987:Gonadotropin-Releasing Hormone