CATABOLISM OF LOW-DOSE HEPARIN IN MAN

An iodinated heparin derivative was injected with carrier heparin into healthy volunteers. The iodinated material was of similar MW to the underivatized heparin, highly sulfated and biologically active. It bound to plasma proteins including antithrombin III in vivo, and more than 85% was firmly bound to platelet factor 4 or protamine in vitro. After injection of 1-100 units, 80-90% was removed from the plasma within 40 min, most of it being sequestered by the liver and some by the spleen, lungs and kidneys. Iodinated material was then again released into the plasma. The MW of this product was unchanged, but it was no longer biologically active. It was not bound to antithrombin III in vivo, or to platelet factor 4 and protamine in vitro, and it was markedly desulfated. Except at doses greater than 1000 units, the labeled material was degraded to small fragments before excretion in the urine.