Seasonal variations of blood haptoglobin level of brown bears in Japan

Haptoglobin (Hp), a hemoglobin-binding protein, is known as an acute phase protein increasing in blood during inflammation in most mammals. On the basis of our previous studies on purification and characterization of bear Hp (Comp. Biochem. Physiol. 110B, 785-789, 1995), in this study, we developed an immunoassay method to measure serum Hp level in bear, and measured the concentration of Hp in blood samples collected from 84 reared and 25 wild brown bears in Hokkaido, Japan. The mean serum Hp concentration was 0.94 ± 0.25 mg/ml in wild bears, which is nearly equal to those reported in other species. In reared bears, the Hp concentration was apparently higher (3.82 ± 0.29 mg/ml), although total protein and albumin concentrations were nearly equal in the two groups. A significant seasonal variation of serum Hp, low in spring and high in autumn and winter, was found in reared bears. Possible factors participating in the seasonal variation were discussed with special references to hibernation.