Restoration of low casein feed-induced decrease in serum erythropoietin concentration by fortifying diet with methionine and threonine in normal and nephritic rats

Erythropoietin (EPO) is a glycoprotein that stimulates red blood cell produ ction and the kidney is the major source of EPO production. We examined the effects on serum EPO concentration of a low (8.5%) casein diet (8.5C), nep hritis induction, and supplementation of the limiting amino acids, 0.3% L-m ethionine and 0.36% L-threonine, to the low casein diet (8.5CMT), using a 2 0% casein diet (20C) as the control. Nephritis was induced in rats by an in travenous injection of anti-rat kidney glomerular basement membrane rabbit antiserum. Serum EPO concentration decreased when normal rats were fed the 8.5C, and this decrease was quickly restored when refed the 20C or 8.5CMT. Serum EPO concentration was significantly lower in 20C-fed nephritic rats t han in 20C-fed normal rats. In the nephritic state as well as the normal st ate, serum EPO concentration was significantly decreased in the 8.5C-fed an imals compared with the 20C-fed ones. This fall in serum EPO was restored t o the concentration of 20C-fed rats by 8.5CMT feeding. The 8.5CMT also redu ced proteinuria and hypercholesterolemia in nephritis without the severe gr owth retardation. These results suggest that the dietary manipulation of 8. 5CMT has a diversity of beneficial effects on nephritis. (C) 2000 Elsevier Science Inc.