AJP - Regulatory, Integrative and Comparative Physiology, Vol 260, Issue 2 177-R184, Copyright © 1991 by American Physiological Society
Branched-chain amino acids augment neither albuminuria nor albumin synthesis in nephrotic rats
G. A. Kaysen, H. al-Bander, V. I. Martin, H. Jones Jr and F. N. Hutchison
Department of Medicine, Veterans Affairs Medical Center, Martinez 94553.
Both albuminuria (UalbV) and albumin synthesis (AlbSyn) are modulated by
dietary protein in nephrotic rats, but the agent(s) linking diet to altered
UalbV 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 UalbV is unknown. Because BCAA
increase AlbSyn in tissue culture and after a fast, it is possible that
feeding BCAA may increase AlbSyn but not UalbV 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). UalbV 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 UalbV.
The ability of dietary protein to increase AlbSyn or UalbV 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
UalbV.
