Effect of an L-arginine-reduced diet on proteinuria and hyperlipidemia in rats with anti-glomerular basement membrane nephritis

We examined whether or not elimination of L-arginine from a standard 20% casein diet would improve proteinuria and other symptoms in glomerulonephritic rats. Casein was enzymatically digested by trypsin and carboxypeptidase B. This enzymatical digestion of casein reduced the contents of L-arginine, L-lysine and L-histidine. The digested casein supplemented with L-histidine and L-lysine to the original casein levels was designated as enzymatically modified casein (EMC), and EMC supplemented with L-arginine to the original casein level as EMC+Arg. Male Wistar rats with glomerulonephritis induced by a single intravenous injection of nephrotoxic serum were fed either a 20% EMC+Arg (control) diet or 20% EMC (arginine-reduced) diet for 9 days. Nephritic rats fed the control diet showed not only proteinuria but also hyperlipidemia. Feeding EMC ameliorated proteinuria and hyperlipidemia without restriction of protein intake. These results suggest that trials to reduce dietary L-arginine even in standard protein diets have a remedial effect on the symptoms of glomerulonephritis.