Abstract
The calcium-binding activity in the soluble fraction of a normal rat liver was studied. Calcium binding in the supernatant depends on the competition between a cation-exchange resin and a soluble calcium-binding substance for added calcium. The calcium concentration found in the supernatant of the test system was approximately 12-fold of that of calcium contained in the soluble fraction of a normal rat liver. The binding of calcium in the supernatant of the test system using the heat-treated soluble fraction increased linearly up to 0.75 mM calcium and was saturated 1.0 mM calcium. When the radiocalciumbinding activity was expressed as S/R net, the radiocalcium-binding activity existed in soluble fraction, and it increased approximately 4-fold by the heat treatment. These results suggest that the calcium-binding factor exists in the soluble fraction of a normal rat liver.
