Measurement of the rate of synthesis of albumin with 14C-carbonate: a simplified method.

A simplified method for the determination of the rate of synthesis of albumin after the i. v. injection of C-carbonate is described. A number of experiments to check the accuracy of the CO2 measurements is reported. Good agreement is obtained between the specific activity of urinary urea, measured by means of our method and by the manometric method. Recoveries of 101.9 and 101.1% respectively are found for C-urea added to plasma or urine. Endogenously formed C-urea shows a maximal specific activity 2—3 h after the i. v. injection of C-carbonate. Thereafter the specific activity of C-urea gradually decreases. Enzymic conversion with arginase and urease and analysis with an amino-acid analyser give the same values for the arginine content of an albumin hydrolysate. Good agreement between the rates ot synthesis and catabolism of albumin, determined respectively with C-carbonate and I-albumin, was obtained in individual patients. In a group of 6 patients an average rate of synthesis of 10.6 mg/kg · h and an average catabolic rate of 9.5 mg/kg · h were measured. The difference between this simplified method and the manometric technique lies in a direct measurement of the concentration of urea and arginine in the method described here in contrast to the conversion of urea and arginine to CO2 in the manometric method. Advantages of the simplified method for the determination of the rate of synthesis of albumin are discussed.