EXPRESSION OF NA-H+ EXCHANGER ISOFORMS NHE1 AND NHE3 IN KIDNEY AND BLOOD-CELLS OF RABBIT AND RAT()

Increased peripheral blood cell Na-H exchange (NHE) and erythrocyte Na -Li countertransport activity have been reported in hypertension and d iabetic nephropathy and correlated with increased activity of the rena l brush border Na-H exchanger. A relationship between cation exchange activities of blood cells and renal brush border membranes might exist if both were mediated by the same NHE isoform. We generated isoform-s pecific antibodies to compare the expression of NHE1 and NHE3 in perip heral blood cell membranes and renal cortical membrane vesicles. An NH E1-specific monoclonal antibody reacted with a 199- to 110-kD protein in basolateral membrane fractions isolated from rabbit and rat kidney. NHE1 protein expression was also detected in erythrocytes, platelets, and lymphocytes isolated from rabbit and rat. Two polyclonal antisera generated against nonoverlapping portions of NHE3 reacted with protei ns of 82 and 85 kD in brush border membrane fractions isolated from ra bbit and rat kidney, respectively, but failed to detect NHE3 expressio n in blood cells. These data do not support the hypothesis that Na-H e xchanger of Na-Li countertransport in blood cells takes place via the renal brush border membrane NHE isoform, namely NHE3.