The Effect of Amino Acids on Serum and Urine Creatine.

There is now unequivocal evidence that creatine is formed from glycine, arginine, and methionine (1). It is equally well established that creatine can be transformed into creatinine and excreted in this form by the kidneys (2). Creatine is also concerned with the intermediary metabolism of carbohydrate. By a photometric modification of Folin's method, devised by Peters (3), Tierney and Peters (4) demonstrated that the serum of normal men contained measurably significant amounts of creatine. They found that the serum creatine was elevated in patients with hyperthyroidism. Creatinuria was almost invariably associated with concentrations of serum creatine greater than 0.6 mgm. per cent, suggesting that creatine, presumably filtered in the renal glomeruli,. is completely reabsorbed in the tubules when its concentration in the serum is less than 0.6 mgm. per cent. The present paper deals with the serum creatine and creatine excretion in various pathological conditions and after certain induced physiological disturbances.