Fig. 4.

Effect of dietary protein restriction on NHE3 and NKCC2 expression. Top: effects of 6% (low-protein) and 20% (normal protein) diet on expression of the proximal tubule apical Na⁺/H⁺ exchanger NHE3. NHE3 is believed to be the major mechanism of proximal tubule ammonium secretion. There was no significant change in NHE3 expression in response to low-protein diet. Bottom: effects of dietary protein restriction on expression of NKCC2, the primary protein responsible for luminal ammonium reabsorption by the thick ascending limb. There was no significant change in NKCC2 expression in response to low-protein diet. Values are means ± SE; n = 12/group.