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We devised a clinical test of renal metabolism based on the synthesis of guanidinoacetic acid from citrulline in the proximal convoluted tubule. Intravenous administration of a citrulline/creatine solution to rats with modified levels of renal glycine amidinotransferase activity revealed a strong correlation (r = 0.921) between this activity and urinary guanidinoacetic acid excretion. Citrulline (1.75 […]

Guanidinoacetic acid, a precursor of creatine, is an essential substrate for muscle energy metabolism. Since guanidinoacetic acid has been reported to be synthesized from arginine and glycine by glycine amidinotransferase (transamidinase) in kidney homogenates or slices, the purpose of this study was to provide evidence of guanidinoacetic acid synthesis in isolated tubules from rat kidneys, […]

A method was developed for evaluating the relative rate of conversion of [14C]-citrulline to [14C]arginine in vivo. By this method it was demonstrated that the conversion was almost completely abolished by functional nephrectomy, but not by functional hepatectomy. It was also demonstrated that functional nephrectomy caused a prompt increase in the citrulline concentration in the […]

The concentration of methylguanidine and guanidinosuccinic acid has been measured in normal human plasma and discrepancies between various published methods for measuring methylguanidine have been resolved. Previous methods have been modified to allow these guanidines, together with guanidinoacetic acid and creatine, to be measured on the same serum sample. Mean values in six normal subjects […]

Several investigators established that 2 enzymes are involved in biosynthesis of creatine. Arginine + glycine = guanidinoacetate + ornithine. Guanidinoacetate + S-adenosylmethionine = creatine + S-adenosyl- homocysteine. The first enzyme, arginine- glycine transamidinase, has long been known to occur in mammalian kidney , while the second enzyme, guanidinoacetate methylferase, has been found in liver. [TRUNCATED] […]

Guanidoacetic acid is an important precursor of creatine in the organism. Other than this, little is known regarding the metabolism of this compound. Guanidoacetic acid is formed in the body by the transfer of the amidine group of arginine to glycine according to the following reaction, arginine + glycine = guanidoacetic acid + ornithine, which […]

The synthesis of creatine from guanidinoacetic acid in liver was originally demonstrated by Borsook & Dubnoff, and these authors later concluded that guanidinoacetic acid was not a normal constituent of that organ. This conclusion was confirmed by Bodansky, Duff & McKinney, who reported that no guanidinoacetic acid could be detected in normal animals. [TRUNCATED]. Rosenberg […]

The purpose of this report is to record the quantitative urinary excretion of glycocyamine, creatine and total creatinine by a group of normal infants and children. Flood RG, Pinelli RW. Urinary glycocyamine, creatine and creatinine; their excretion by normal infants and children. Am J Dis Child. 1949 Jun;77(6):740-5.