Comparison of methods for the measurement of human protein synthesis

The rate of protein synthesis in one subject was measured four times with [¹⁵N]glycine as the tracer. Two pulse-label and two continuous-infusion experiments were done. The two pulse-label experiments gave significantly higher protein synthesis rates (49.7 and 39.8 mg of N/kg body wt/hr) than the continuous-infusion determinations (26.2 and 22.4 mg of N/kg body wt/hr). As an independent test of the validity of the continuous-infusion approach, the rate of protein synthesis in the rat was measured by the continuous-infusion method. The value of 74 mg of N/kg body wt-hr agrees well with literature estimates of rat protein synthesis.