Opiate receptors are present in the rat testis. Identification and localization in Sertoli cells.
We have characterized opioid binding sites in the Sertoli cells of adult and 18-day-old rat testes. Maximal specific etorphine binding was attained after 30 min at 4 C. The binding was reversible, with association and dissociation rate constants of 0.98 X 10(5) M-1 min-1 and 0.33 min-1, respectively. Scatchard analyses and saturation curves revealed a single class of high-affinity, low-capacity binding sites. No opioid binding was observed in Leydig cell cultures. Exposure to opioids for 3 days caused a significant increase in [3H]etorphine specifically bound to the Sertoli cells that was completely prevented by naloxone, demonstrating opioid up-regulation of its own receptor. Chronic opioid treatment of the cultures significantly inhibited androgen-binding protein production, and this effect was prevented by naloxone. Since the circulating concentrations of endorphins (10(-12) M) are lower than the Kd of testis opiate receptors, it is conceivable that opioids of Leydig cell origin act on the specific high-affinity receptors of the Sertoli cells, and may play a role in modulating their function.
D000727:Androgen-Binding Protein / Q000378:metabolism; D000818:Animals; D005048:Etorphine / Q000378:metabolism; D007700:Kinetics; D008297:Male; D009270:Naloxone / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D011957:Receptors, Opioid / Q000032:analysis*; D012708:Sertoli Cells / Q000032:analysis*; D013696:Temperature; D013997:Time Factors
D000727:Androgen-Binding Protein; D011957:Receptors, Opioid; D009270:Naloxone; D005048:Etorphine