Modulation of Testicular and Whole Blood Trace Element Concentrations in Conjunction with Testosterone Release Following Kisspeptin Administration in Male Rabbits (Oryctolagus cuniculus)

The present study investigated the role of kisspeptin-10 on reproductively significant trace elements in relation to testosterone release in male rabbits, Oryctolagus cuniculus. Groups of rabbits were exposed to single 1 mu g kisspeptin dose (i.v., saphenous vein), while simultaneous groups were pretreated with a kisspeptin antagonist, peptide-234 (50 mu g)20 min before administering kisspeptin. Sequential blood sampling was done through marginal ear vein puncture at staggered time intervals: 0, 0.5, 1, 2, 4, and 24 h to determine serum testosterone. Testes and whole blood were collected at 4 and 24 h post dosage to determine trace element concentrations through atomic absorption spectrophotometry. In testes, zinc (Zn), manganese (Mn), and Fe concentrations showed significant increases at 24 h, while copper (Cu) concentration was found elevated at 4 and 24 h both (P<0.001). In whole blood, Zn and Cu concentrations were significantly elevated at 4 and 24 h, while Mn and cobalt (Co) concentrations showed increases only at 24 h (P<0.001). Blood iron concentration was not altered in the blood. In contrast, no change occurred in testicular Co, and chromium or nickel concentrations in either testes or blood. Compared to control and predose groups, serum testosterone levels increased gradually and peaked at 2 h (P<0.001) post kisspeptin treatment but declined thereafter. Pretreatment with antagonist abolished all increases in trace elements and testosterone concentrations. The present study provides first evidence that reproduction-and fertility-related peptide "kisspeptin" modulates testicular and blood trace elements and that this action is likely GPR54-dependent.