Peripheral administration of the human kisspeptin-10 and 26RF-amide inhibits plasma testosterone levels in the adult male broiler breeder birds (Gallus domesticus)

Kisspeptin (KP), a family (belonging to the RFamide superfamily of peptides) of related-peptide hormones encoded by the KISSI gene, is recently identified as the major player in the neuroendocrine regulation of the mammalian reproduction. Despite the well established role of KP in mammals not much is known about their action in non-mammalian species especially in the avian reproductive physiology. Therefore, the present study was designed to examine the effect of peripheral administration of human kisspeptin-10 (KP10) on the plasma testosterone (T) concentration in the broiler breeder birds. Three different doses (11.5, 23, 38-nmol; intravenous injection) of KP10 were tested in the intact adult male broiler breeder birds under normal fed conditions. In addition, hCG (30U) and vehicle (0.5 ml) were administered for control purposes. A single dose (38-nmol) of human 26RFamide (26RFa; another member of RFamide superfamily) was also tested. KP10 administration dose-dependently inhibited (P less than 0.05-0.005) plasma T levels. Likewise, 26RFa administration also significantly decreased (P less than 0.05) plasma T concentration. Vehicle administration did not alter plasma T levels. hCG administration stimulated (P less than 0.01) plasma T levels. Thus, the present study demonstrat6d that human KP10 and 26RFa administration suppressed plasma T levels in the adult male broiler breeder birds. Our findings of the present study, therefore, assign a novel role to KP10 and 26RFa, as inhibitor of plasma T secretion in the broiler breeder birds. However, the mechanisms (receptor and intracellular signaling) by which KP10 and 26RFa suppressed the plasma T level in the broiler breeder birds are currently unknown.