Factors which affect urea synthesis and handling are examined in RJS. BUN and blood ammonia are increased in untreated patients but no correlation between these two metabolites was found. In fatal outcomes a two-fold rise in the peak BUN was frequently seen. The total plasma amino acid concentration in RJS is nearly three and one-half times that of control subjects reflecting the increased amino acid load presented to the liver for processing. The total plasma amino acid concentration in untreated patients is even higher than that observed in a patient with liver failure. A significant reduction in arginine and an increase in ornithine levels are found in many patients. Ornithine is not a significant component of muscle actinmyosin protein whereas arginine is present nearly to the same extent as lysine. These findings suggest that the hydrolysis of arginine from the breakdown of protein by arginase (reportedly normal or increased in activity in RJS) could contribute to urea formation. Glomerular filtration rates as determined by creatinine clearances are both low and high in untreated patients. The urinary excretion of urea based on creatinine is nearly twice that of sick controls in untreated patients. Na and K excretion at comparable urine osmolarities are significantly diminished in untreated RJS patients. A peculiar pattern of an abrupt drop in urea excretion despite the presence of increased urea in the blood as well as the observation of a similarly acute drop in urea excretion in a child with varicella are presented and discussed in the light of observations of increased vasopressin levels in RJS patients above stage I.
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