Fig. 6.

Effect of dietary protein restriction on residual glutamine synthetase expression in PT-GS-KO mice. Previous studies showed residual glutamine synthetase expression in mice with PT-GS-KO, both in the proximal tubule and in distal epithelial cells (16). Left, immunoblot analyses show that dietary protein restriction significantly increases residual glutamine synthetase expression in the renal cortex. Data were normally distributed in both cortex and OSOM, and Student’s t-test was used for statistical analysis. Right, immunohistochemistry findings in PT-GS-KO fed 20% or 6% protein diet for 7 days. Glutamine synthetase expression in proximal tubule cells that was not deleted by this gene-targeting approach is evident (*). GS immunolabel intensity in these proximal tubule cells was increased in response to 6% protein diet. Results are representative of findings in 6 mice in each group. CD, collecting duct segments.