Urea metabolism in an azotaemic woman with normal renal function

The blood-urea of a 43-year-old woman with normal renal function was 150 mg. per 100 ml. because she regularly consumed about 400 g. of protein daily. She had no symptoms of uraemia and her haemoglobin concentration was normal. Although she had a very large body-urea pool she degraded no more urea than healthy individuals on a normal diet. The failure of endogenous urea hydrolysis to increase in proportion to the blood-urea in renal failure has tentatively been ascribed to toxic effects of compounds retained with urea in renal failure; the findings in this azotaemic patient, who had neither signs nor symptoms of uraemia, cast doubt upon that explanation.

Efficiency of utilization of urea nitrogen for albumin synthesis by chronically uraemic and normal man

1. The relation between endogenous urea metabolism and albumin synthesis has been studied in ten patients with chronic renal failure and in four normal subjects, after single intravenous injections of [14-C]urea,[15-N]urea and 125-I-labelled albumin. 2. The rate of urea synthesis was determined from the dynamics of plasma [14-C]urea specific radioactivity and the rate of urea metabolism was estimated from the relative rates of urea synthesis and urea appearance in urine and body water. Deconvolution analysis of plasma [15N]albumin enrichmevt and 125-i-labelled albumin radioactivity yielded the cumulative incorporation of 15-N into total exchangeable albumin and enabled calculation of the absolute rate of urema nitrogen utilization for albumin synthesis. 3. Although the mean absolute rate of urea degradation in uraemic patients (3-7 mmol/h) was higher than in normal subjects (2-3 mmol/h) there was no significant positive correlation between urea degradation and plasma urea concentration. 4. In uraemic subjects, there was a significant positive correlation between urea synthetic rate and urea degration rate. 5. The rate of utilization of urea nitrogen for albumin synthesis was low, but was very much higher in uraemic subjects (mean 83-8 mumol/h) compared with normal subjects (mean 6-4 mumol/h), as was the provision by urea of the nitrogen required for albumin synthesis in uraemic subjects (2-37%) compared with normal subjects (0-13%). 6. The efficiency of utilization of urea nitrogen for albumin synthesis was higher in the uraemic patients (1-3%) than the normal subjects (0-2%), and was higher in those patients with chronic renal failure who received a 30 g protein diet than those on 70 g of protein. A significant negative correlation was noted between efficiency of urea nitrogen utilization and the rate of synthesis of albumin. 7. These studies suggest the presence of a mechanism for the conservation of urea nitrogen in chronic renal failure which is unrelated to the extent of urea degradation, and which can only be partly explained by the higher proportion of intraluminal gut nitrogen derived from urea.

Thallium-201 for medical use. I

Thallium-201 merits evaluation for myocardial visualization, kidney studies, and tumor diagnosis because of its physical and biologic properties. A method is described for preparation of this radiopharmaceutical for human use. A critical evaluation of 201Tl and other radiopharmaceuticals for myocardial visualization is given.

Protein metabolism in uraemia

Protein metabolism in uraemia is reviewed. Very few, if any, disorders of amino acid metabolism can at present confidently be attributed to uraemia per se rather than to protein/energy deprivation. Retained urea nitrogen is recycled to the liver as ammonia; a proportion is reutilized for synthesis of non-essential amino acids and, if their carbon skeletons are supplied, for synthesis of essential amino acids. Practical applications of the reutilization of non-amino nitrogen in advanced chronic renal failure are being explored. Nevertheless, uraemic individuals readily become undernourished, and they should receive as much protein as their symptoms will permit.

Reversal of rapidly progressive renal failure associated with polyarteritis

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Acute ileostomy diarrhoea with incipient renal failure due to fish tapeworm infestation

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Periodic hypokalaemic paralysis, adrenal adenoma, and normal colonic transport of sodium and potassium

A 47-year-old woman was cured of hypokalaemia and recurrent paralysis by the excision of an adrenal adenoma. Hypertension was initially ameliorated but was not cured. Suppression of plasma renin activity was abolished when the adenoma was excised. Repeated measurement of plasma corticosteroids before operation showed a slight increase in aldosterone and normal plasma concentrations of deoxycorticosterone, corticosterone, and cortisol. No evidence of excess mineralocorticoid was obtained from measurement of the electrolyte composition of colonic fluid or of rectal potential difference, although both these variables responded normally to salt depletion and exogenous aldosterone. The diagnostic importance of the paradoxically normal colonic measurements is emphasized and the possibility is considered that the adenoma may have secreted an unidentified hormone.

The effects of low-protein diet and uraemia upon urea-cycle enzymes and transaminases in rats

1. Activities of arginine synthetase system enzymes, alanine aminotransferase (AlT) and branched-chain amino acid transaminase (BATase) were measured in control and uraemic rats after 2 weeks on a free protein intake and after 10 days on a low-protein diet.

2. Protein restriction alone reduced the activity of all three enzymes.

3. Uraemia alone increased the activity of arginine synthetase system enzymes and AlT. BATase was not altered.

4. After protein restriction the BATase activity in uraemic rats decreased to the same extent as in controls. The activity of arginine synthetase system enzymes and AlT were significantly higher than in protein-restricted controls and were the same as in control rats on a normal diet.

5. Practical consequences of the finding that uraemia prevented the decrease of AlT but not of BATase activity in response to a low-protein diet are discussed, with particular reference to reutilization of urea-nitrogen for the synthesis of non-essential and essential amino acids.