In vitro effects of beta-endorphin on testicular release of androgens in the lizard Podarcis sicula Raf.
The effects of the proopiomelanocortin-derived opioid peptide, beta-endorphin (beta-EP), and of the opioid antagonist, naloxone (NAL), on both basal and pituitary-stimulated androgen secretion from superfused quiescent and active testes were assessed in the adult lizard, Podarcis sicula. In the absence of the homologous pituitary, in vitro treatment with beta-EP and/or NAL did not affect basal secretion of androgens from quiescent and active testes. Conversely, in the presence of the homologous pituitary, treatment with beta-EP brought about a decrease in androgen secretion in active testes, but no effect on quiescent ones. Naloxone counteracted the inhibitor effect of beta-EP in active testes, and enhanced maximal pituitary-stimulated secretion of androgens in quiescent but not in active testes. The effects produces by beta-endorphin and naloxone were reversible. These results suggest that, in this lizard, opioids might be involved in the control of androgen release. The lack of effect of beta-EP and naloxone when added directly to the testes seems to suggest that the opioid agonist and antagonist act on androgen release by modulating pituitary gonadotrophin output.
Ciarcia
G
G
Department of Zoology, University of Naples Federico II, Italy.
Cardone
A
A
Paolucci
M
M
Botte
V
V
D000728:Androgens / Q000096:biosynthesis*; D000818:Animals; D066298:In Vitro Techniques; D008116:Lizards; D008297:Male; D009270:Naloxone / Q000494:pharmacology*; D009292:Narcotic Antagonists / Q000494:pharmacology*; D009294:Narcotics / Q000494:pharmacology*; D010902:Pituitary Gland / Q000378:metabolism; D013737:Testis / Q000187:drug effects / Q000378:metabolism*; D001615:beta-Endorphin / Q000494:pharmacology*
D000728:Androgens; D009292:Narcotic Antagonists; D009294:Narcotics; D009270:Naloxone; D001615:beta-Endorphin