Annual changes in serum leptin concentration in the adult female Japanese black bear (Ursus thibetanus japonicus)

In the present study, assay of the serum leptin concentration of the Japanese black bear (Ursus thibetanus japonicus) was attempted using a canine-leptin-specific sandwich enzyme-linked immunosorbent assay (ELISA). The dose-response curve of the bear serum was linear and parallel to the canine leptin standard curve. In mated and unmated bears, the serum leptin concentration was stable at low levels from May to August or September, gradually increased from September or October, and then remarkably increased in late November. We conclude that this method may be useful for measuring bear serum leptin concentration and that the serum leptin concentration changes annually with a peak in late November.