1. A 1% amino acid dialysis solution with a high concentration of the branched-chain amino acids has been compared with 1.36% glucose in short-term studies. 2. The 1% amino acid solution was as effective an agent as 1.36% glucose with respect to ultrafiltration and clearance of creatinine, urea and potassium. 3. Levels of branched-chain amino acids rose to the upper end of the normal range within 1 h and remained at this level over the entire period of the study. Total and non-essential amino acids had returned to baseline by the end of the cycle. 4. Blood glucose rose to significantly greater levels during the 1.36% glucose exchange than during the 1% amino acid exchange. There was an increase in serum insulin levels during both cycles; this was significantly greater with the 1% amino acid solution than the 1.36% glucose. 5. There was no evidence of short-term metabolic complications with the 1% amino acid solution.

We studied the effects of bilateral nephrectomy on bone metabolism in 27 patients on maintenance hemodialysis. After nephrectomy plasma alkaline phosphatase fell rapidly in 10 patients whose preoperative plasma levels had been higher than normal. This fall was associated with a transient decrease in osteoblast counts of iliac-bone biopsies. A fall in plasma phosphate and a rise in plasma immunoreactive calcitonin also occurred, but calcium and immunoreactive parathyroid hormone levels did not change. Alkaline phosphatase levels remained unchanged in a control group of 17 patients on dialysis who had undergone an operation other than nephrectomy. In 26 nonsurgical patients on dialysis, immunoreactive calcitonin was inversely related to osteoblast counts. Rises in immunoreactive calcitonin may be partly responsible for the transient decreases in bone turnover after bilateral nephrectomy. Low levels of endogenous calcitonin may allow an increase in bone turnover in chronic renal failure.

Thirty-five patients with bone disease and chronic renal failure (twenty-four on maintenance haemodialysis) were treated for 7--39 months with 1alpha-hydroxyvitamin D3, 2--2.5 microgram daily by mouth. Symptoms (bone pain and muscle weakness) and radiographic appearances improved and plasma alkaline phosphatase returned to normal in the majority of patients (87, 76 and 75% respectively). In contrast, histological appearances in bone improved in only 46% twenty-three patients from whom paired biopsies were available, and this change was not greatly different from that seen in a comparable group of untreated patients. Significant correlations were noted in individual patients between the changes in symptoms, X-rays, plasma alkaline phosphatase and immunoreactive parathyroid hormone and these, in turn, were related to histological changes in bone, although these latter changes were often small. It is concluded that 1alpha-hydroxyvitamin D3 is a useful new drug in the treatment of renal bone disease, but that the evaluation of the response depends critically on the method of assessment used.

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