Measurement of half-life of human plasma fibrinogen

¹ Surgical Research Laboratories, Graduate Hospital of The University of Pennsylvania and Harrison Department of Surgical Research, University of Pennsylvania, Philadelphia, Pennsylvania, 19146

The plasma fibrinogen half-life (t_1/2) was measured in a series of adult volunteers by feeding either [¹⁵N]glycine (100–350 mg/h) or [¹⁵N]ammonium chloride (180–350 mg/h) plus sodium benzoate (250–500 mg/h). The ¹⁵N enrichment of the hepatic fibrinogen amino acid precursor pool was estimated from the ¹⁵N enrichment of the urinary hippuric acid. The amount of isotope incorporated into fibrinogen was found by measuring the ¹⁵N enrichment of glycine incorporated into fibrinogen. Two types of experiment were run. i) Initial-rate: the subject took the [¹⁵N]glycine or [¹⁵N]ammonium chloride plus benzoate mixture orally in eight equal doses over a 3- to 4-h period. ii) Steady-state: the [¹⁵N]glycine or [¹⁵N]ammonium chloride plus benzoate were taken orally in 10 equal doses over a 10- to 12-h period. Giving the isotope at a constant rate results in an approximate isotopic steady state in the body's free amino acid pools. For both types of experiment a blood and urine specimen were obtained at the end of the ¹⁵N feeding period. The results of the experiments were: t_1/2 (days), initial-rate with [¹⁵N]glycine, 3.4 ± 1.5 (7), t_1/2 with [¹⁵N]ammonium chloride, 1.4 ± 0.6 (7); t_1/2 steady-state with [¹⁵Nlglycine, 2.4 ± 0.6 (5), and with [¹⁵N]ammonium chloride 1.6 ± 0.4 (5). The numbers in parentheses are the numbers of studies. The values obtained with [¹⁵N]glycine were greater than the corresponding [¹⁵N]ammonium chloride values. (P < 0.02 for both methods.)

protein synthesis; ¹⁵N

Submitted on January 3, 1977