Dose-response study with canine kisspeptin-10 in vivo and in vitro

Abstract

Kisspeptin stimulates gonadotropic-releasing hormone (GnRH) and is a key player in puberty onset and maintenance of normal reproductive function in several mammalian species. However, doses below 1 μg/kg BW have not been studied in dogs. The aims of this study were to find the lowest dose of canine kisspeptin-10 that significantly increases the plasma LH concentration above the 95 percentile of the measured basal plasma LH concentrations in dogs and to investigate the corresponding effects of human kisspeptin-10 (hKP10) and canine kisspeptin-10 (cKP10) in vitro. cKP10 was administered intravenously at weekly intervals to adult Beagle bitches during anestrus in doses of 0.1, 0.5, 1 and 10 μg/kg BW. Blood samples were collected at 40 and 0 minutes before and at 10, 20, 30, 40, 60, 90, and 120 minutes after KP10 administration for measurement of plasma LH concentration. The doses 0.5, 1 and 10 μg/kg BW resulted in an increase in plasma LH concentration above the 95 percentile of the measured basal plasma LH concentrations. Chem-1 cells transfected with GPR54 cDNA were exposed to 10-6,10-8 or 10-10 M hKP10 or cKP10 and the maximum amplitude of intracellular Ca2+ concentrations, [Ca2+]i, was calculated for each cell. The maximum amplitudes of [Ca2+]i differed between hKP10 and cKP10 for only 10-8 M. In conclusion, 0.5 μg/kg BW cKP10 is the lowest dose that significantly increases the plasma LH concentration above the 95 percentile of the measured basal plasma LH concentrations in the dog and hKP10 and cKP10 give a similar [Ca2+]i response after binding to the human kisspeptin receptor GPR54 in vitro.