Current emphasis on the use of proteins in the treatment of various disorders of the alimentary tract has stimulated a comparative study of certain aspects of protein metabolism in normal persons and in patients with gastro-intestinal disease. In addition to the usual nitrogen balances, microbiological assays were made of eight amino acids in food, acid-hydrolyzed whole plasma, tungstic acid filtrates of plasma (free amino acids), acid-hydrolyzed tungstic acid filtrates of plasma (free plus combined amino acids),' hydrolyzed urine, and in feces. The amino acids measured were methionine, lysine, arginine, histidine, leucine, isoleucine, valine and threonine. The Subject 2, R. G. H.; initial weight was 84 kg., height 187 cm. The basal metabolic rate was 0; basal calories were estimated as 1990. The blood and plasma volumes were measured by the Gibson-Evans method (15) at frequent intervals in this subject; the values were relatively constant, averaging 6198 and 2720 cc., respectively.
B. DietNormal activity was permitted. Fluids were allowed ad libitum, but the fluid intake and urine output were measured daily. The only medication consisted of a liquid vitamin B preparation given daily. Though the quantity of protein was varied, the caloric intake was kept uniform by adjustment of the carbohydrate and fat content of the diet. The number of calories was determined on the basis of the basal metabolic rate of each subject, with additional allowances for his usual activity. In Subject 1, the intake of calories was 3200, the carbohydrate ranging in the various periods from 403 to 477 gms. and the fat from 110 to 154 gms. In Subject 2, the intake of calories was 3190, the carbohydrate ranging from 415 to 475 gms. and the fat from 103 to 131 gms. Two to 4.0 gms. of table salt were added to the food each day. Crystalline methionine was added in periods 9 and 10; in all other periods the quantity of individual amino acids was varied by changes either in the amount or type of protein. Following a transitional interval of three days, each regimen was studied for two consecutive six-day periods.
C. Preparation and Analysis of Food, Plasma and UrineThe food was prepared in the kitchen of the metabolism section by dietitians trained in the problems of metabolic research. The food was weighed on a torsion balance before cooking; salt was the only seasoning; meats were broiled. The quality and quantity of the food were kept uniform throughout each regimen.For analysis, a 30 to 40 per cent aliquot of a one-day supply of food (excepting pure carbohydrate and fat) was homogenized with distilled water in a Waring blendor. A second aliquot of the same diet was prepared and analyzed approximately one week later; the results of both measurements were averaged.At the end of each six-day period, following a 10-hour overnight fast, 100 ml. of venous blood were drawn, transferred to a screw-capped bottle containing 15 to 30 mg. of heparin, and mixed thoroughly. The blood was centrifuged and the plasma removed immediately. One-716
