Effect of dietary protein on renin and angiotensinogen gene expression after renal ablation

High dietary protein increases renin mRNA and likely contributes to the increased plasma renin activity (PRA) in the normal rat. In experimental renal ablation, dietary protein influences renal growth and injury. This study was undertaken to examine the effect of dietary protein on the renin-angiotensin system after reduction of renal mass. Male Sprague-Dawley rats were subjected to 1 1/3 nephrectomy (1 1/3 NX) and maintained for 7 days on a low-protein (6%) diet, at which time they were stratified according to serum creatinine to either continue on the low-protein diet or were switched to a high-protein (40%) diet. Two weeks after stratification renal renin mRNA was higher on the 40% compared with the 6% protein diet, angiotensinogen mRNA was lower in the high-protein group, and no change occurred in renal actin mRNA. The magnitude of this dietary protein-induced increase in renin mRNA with high-protein diet was greater in the 1 1/3 NX group compared with that observed in sham-operated rats (320 vs. 60%). PRA and tissue renin activity were also elevated on the high-protein diet after 1 1/3 NX. When three levels of dietary protein intake were examined after 1 1/3 NX, the high-protein (40%) diet was associated with increased renal renin mRNA compared with both the intermediate-protein (20%) and low-protein (6%) diets. In conclusion, a high-protein diet induced activation of the renin-angiotensin system. This activation may explain some of the detrimental effects of dietary protein on the course of chronic renal failure.