Amino Acid Administration Enhances Renal Protein Metabolism after Acute Tubular Necrosis

Abstract

The capacity of exogenous amino acids to alter renal protein metabolism was studied during renal regeneration after mercuric chloride-induced acute tubular necrosis in the rat. In regenerating cortical tissue, the free leucine concentration was 17% lower than normal, and was decreased further after glucose infusion. The concentration was raised above normal by amino acid infusion thereby ameliorating the deficit of this amino acid. Synthesis and degradation of rapidly-turning over proteins in renal cortical cells was examined in vitro. Renal protein synthesis in cortical slices was assessed by measurements of tissue leucine specific radioactivity and cycloheximide-inhibitable [¹⁴C]leucine incorporation into protein. Protein synthesis in regenerating tissue was 52% higher than normal and was not increased further by glucose infusion. In contrast, amino acid infusion increased the rate 47% above that observed after an isocaloric glucose infusion, thereby demonstrating that amino acid enhancement of protein synthesis is superimposed upon the increased synthetic rate observed during renal regeneration. Renal protein degradation remained at the normal rate after amino acid infusion, but was increased in regenerating tissue and after glucose infusion. These results indicate that infused amino acids act on the kidney to enhance protein synthesis and reduce protein degradation in regenerating renal cells after acute tubular necrosis.

Protein Metabolism in Acute Renal Failure

“…Starvation accelerates protein breakdown and impairs protein synthesis in the kidney while refeeding exerts the opposite effect [47]. In the experimental animal, the provision of amino acids or total parenteral nutrition accelerates tissue repair and recovery of renal function [48]. In patients this has been much more difficult to prove.…”

Parenteral Nutrition in Acute Renal Failure

“…The plasma levels of ENAA are reduced in untreated patients [43], dialysis treatment will result in losses of both types of amino acids [45], and, more fundamentally, the availabil ity of sufficient amounts of all amino acids may be criti cal for protein synthesis [46]. In support of this notion is the work of Toback et al [28,47] who found that infusion of an ENAA solution was associated with an increase in renal cell protein and phospholipid synthesis in the mer curic chloride treated rat.…”

“…Further. Toback et al [28] and Toback [29] studied the rate of protein and phospholipid synthesis in renal tissue from rats with mercuric chloride induced ARF and found that the regeneration of renal tissue, as indicated by increased l4C-choline incorporation into membrane phospholipids, is markedly increased as compared to normal renal tis sue.…”

“…The importance of deficient sub strate is suggested by the observations of Toback et al [28] that the level of free leucine in renal cells was decreased in rats with ARF and was restored to normal with amino acid infusion, and the rate of protein synthe sis rose after such infusions. Adequate calorie intake is also important.…”

Acute renal failure in the intensive care unit: adequacy of dialysis and the case for continuous therapies

“…Simple exposure (not dialysis) to cellulosic membranes may result in net protein catabolism [51] which continues for up to 9 h after exposure to the bioincompatible membrane. In addition, the dismal nitrogen balances achieved with standard approaches (lowprotein diet and conventional haemodialysis) to the nutritional management of these patients [52] are unacceptable in view of current thinking in the area of nutrition for the critically ill [53][54][55][56][57][58][59] and acute renal failure [60,61]. With the use of continuous therapies and the increased administration of protein nitrogen, patients with critical illness can move progressively toward the nutritionally important goal of a near neutral nitrogen balance.…”