title: In vivo measurements of body protein based on the determination of nitrogen by prompt gamma analysis.
abstract: Measurement of nitrogen in the human body gives a measure of total protein in the body. Nitrogen (N) may be measured in vivo by a nuclear technique in which the characteristic nitrogen gamma rays emitted after capture of neutrons are detected and counted. The accuracy (as determined by comparison of the measurement of nitrogen in a pig by nuclear and chemical methods) is better than 10%. The reproducibility is less than 6%. The radiation dose is about 5 millirads. This method had been used with 43 patients and 23 normal volunteers and the results are reported. The data are presented in the from of total N content, percentage N by weight, and as a comparison of N and potassium (K) in the body. It is found that the mean percentage of N in the normal males is 2.5%, giving a value of 1.75 kg in the 70-kg standard man. The mean percentage values are not greatly different between normal volunteers and malnourished patients. Taking all subjects, N/K ratios ranged from 7.5 to 20 g/g. Thus K cannot be used as a predictor of N. Nitrogen content of normals correlates well (r = 0.68) with height squared; for malnourished patients there is again a good correlation (r = 0.81) but the regression line for patients is approximately 34% below that for the volunteers consistent with their depleted state.
mesh_terms: D000818:Animals; D001201:Ascites / Q000378:metabolism; D005260:Female; D005720:Gamma Rays; D006801:Humans; D008297:Male; D008722:Methods; D009502:Neutrons; D009584:Nitrogen / Q000032:analysis*; D009587:Nitrogen Isotopes; D009748:Nutrition Disorders / Q000378:metabolism; D009765:Obesity / Q000378:metabolism; D011506:Proteins / Q000032:analysis*; D011829:Radiation Dosage; D013552:Swine
chemical_list: D009587:Nitrogen Isotopes; D011506:Proteins; D009584:Nitrogen