BRANCHED-CHAIN AMINO-ACIDS AUGMENT NEITHER ALBUMINURIA NOR ALBUMIN SYNTHESIS IN NEPHROTIC RATS

Both albuminuria (U(alb)V) and albumin synthesis (AlbSyn) are modulated by dietary protein in nephrotic rats, but the agent(s) linking diet to altered U(alb)V and AlbSyn is unknown. Others have reported that branched-chain amino acids (BCAA) cause neither increased renal blood flow nor glomerular filtration rate (GFR) normally induced by dietary protein nor increased blood glucagon thought to be necessary for protein-mediated effects on renal hemodynamics. The effect of BCAA on U(alb)V is unknown. Because BCAA increase AlbSyn in tissue culture and after a fast, it is possible that feeding BCAA may increase AlbSyn but not U(alb)V in nephrosis. Nephrotic rats were fed either 8.5% casein (LP); 21% casein (NP); 8.5% casein supplemented with valine, leucine, and isoleucine to the total amount provided by a 21% casein diet (2.37%) (LBC); or 8.5% casein plus 12.5% BCAA providing a diet isonitrogenous to 21% casein (HBC). U(alb)V and AlbSyn were significantly greater in NP compared with LP, LBC, or HBC and were the same in the latter three groups. Glucagon was infused into nephrotic rats fed 8.5% casein either subcutaneously or intraperitoneally in quantities sufficient to increase plasma levels to over 10 times control but had no effect on U(alb)V. The ability of dietary protein to increase AlbSyn or U(alb)V is not a result of total alpha-amino nitrogen intake but is a result of the specific amino acid composition of the diet and must result entirely from the effect of one or more non-BCAA. Increased blood glucagon alone has no effect on U(alb)V.