Investigation on interaction of fractionated 3H-heparin with plasma proteins by gel filtration chromatography.

Interaction of fractionated 3H-heparin with plasma proteins was investigated by gel filtration chromatography. The peak of the elution profile for fractionated 3H-heparin in rat plasma was observed at the higher molecular weight fraction than that for fractionated 3H-heparin in buffer without any protein, suggesting the existence of fractionated 3H-heparin binding protein(s) in plasma. Then the interaction of fractionated 3H-heparin with such plasma proteins as albumin, antithrombin III, thrombin and alpha-globulin was investigated. The elution profile for fractionated 3H-heparin in albumin solution, antithrombin III solution and the solution containing antithrombin III and thrombin were different from that for fractionated 3H-heparin in plasma. The elution profile for fractionated 3H-heparin in alpha-globulin solution, of a concentration close to that in plasma, was comparable to that of fractionated 3H-heparin in plasma, though two peaks were found. The major peak corresponded to that of fractionated 3H-heparin in plasma, and the minor peak eluted at a higher molecular weight fraction. When alpha-globulin concentration was decreased, the major peak shifted to the lower molecular weight fraction, and the minor peak was diminished and then disappeared. Thus it was suggested that alpha-globulin is dominant for plasma protein binding of fractionated 3H-heparin.