Characterization of endozepines in the human testicular tissue: effect of triakontatetraneuropeptide on testosterone secretion.
Previous studies have shown that endozepines, i.e. endogenous ligands of benzodiazepine (BZD) receptors, stimulate steroidogenesis in adrenocortical and Leydig cells. In the present report, we have investigated the presence and action of endozepines in the human testis. Immunohistochemical labeling revealed the occurrence of endozepine-like immunoreactivity in Leydig, Sertoli, and germ cells. HPLC analysis combined with a specific RIA resolved two immunoreactive peaks that coeluted with synthetic octadecaneuropeptide (ODN) and triakontatetraneuropeptide (TTN). RT-PCR amplification showed that the mRNA encoding the endozepine precursor diazepam-binding inhibitor is expressed in the human testis. The action of endozepines on testosterone production was studied in vitro using perifused human testicular fragments. Administration of TTN provoked a dose-dependent increase in testosterone secretion, whereas ODN had no effect. The stimulatory action of TTN on testosterone production was totally blocked by flunitrazepam, a peripheral-type BZD receptor antagonist/central-type BZD receptor (CBR) agonist. Conversely, the CBR agonist clonazepam and the CBR antagonist flumazenil did not affect testosterone secretion. Collectively, these results suggest that, in the human testicular tissue, TTN may exert an intracrine and/or paracrine control of steroidogenesis through activation of a peripheral-type BZD receptor.
Duparc
Celine
C
European Institute for Peptide Research, Institut Fédératif de Recherche Multidisciplinaires sur les Peptides 23, Laboratory of Cellular and Molecular Neuroendocrinology, INSERM, Unit 413, CNRS, University of Rouen, Mont-Saint-Aignan, France.
Lefebvre
Herve
H
Tonon
Marie-Christine
MC
Vaudry
Hubert
H
Kuhn
Jean-Marc
JM
D000368:Aged; D001569:Benzodiazepines / Q000494:pharmacology; D026261:Diazepam Binding Inhibitor / Q000378:metabolism*; D006801:Humans; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D008024:Ligands; D008297:Male; D008875:Middle Aged; D009479:Neuropeptides / Q000235:genetics / Q000494:pharmacology*; D010446:Peptide Fragments / Q000235:genetics / Q000494:pharmacology*; D012333:RNA, Messenger / Q000032:analysis; D011963:Receptors, GABA-A / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013737:Testis / Q000187:drug effects* / Q000378:metabolism*; D013739:Testosterone / Q000378:metabolism*
D026261:Diazepam Binding Inhibitor; D008024:Ligands; D009479:Neuropeptides; D010446:Peptide Fragments; D012333:RNA, Messenger; D011963:Receptors, GABA-A; C067529:diazepam binding inhibitor (33-50); C060941:triakontatetraneuropeptide; D001569:Benzodiazepines; D013739:Testosterone