125 I Versus 75 Se Labeling of Fibrinogen for Measuring Turnover of Canine Fibrinogen 1

Abstract

Summary

Apparent turnover of fibrinogen in normal mongrel dogs was observed to be consistently greater when ¹²⁵I-labeled fibrinogen (canine) was used than with the Brodsky technique ([⁷⁵Se] methionine): 4.79 vs 1.96 mg/dl plasma per hour, respectively. When the labeled amino acid was given intravenously to three dogs and their blood was transfused into three other dogs 1-5 days later, only slight differences in fibrinogen turnover were observed between blood donors and recipients, suggesting negligible reutilization of [⁷⁵Se] methionine. It would seem that the ¹²⁵I-labeled fibrinogen was degraded rapidly in vivo because of some intrinsic alteration in the labeled material.