Altered Regulation of type 3 Na(+)/H(+) exchanger, type 1 Na(+)/HCO3 (-) cotransporter, and Na(+),K(+)-ATPase in the Kidney of Rats with Experimental Rhabdomyolysis

Abstract

Metabolic acidosis was shown to correlate with deterioration of renal function in patients with rhabdomyolysis. The present study was aimed to investigate whether the changes of type 3 Na(+)/H(+) exchanger (NHE3), type 1 Na(+)/HCO3 (-) cotransporter (NBC1), and Na(+),K(+)-ATPase α1 subunit may play a role in the pathogenesis of metabolic acidosis in glycerol-induced experimental rhabdomyolysis. Male Sprague-Dawley rats were deprived of fluid intake for 24 hours, and then were injected with 50% glycerol in normal saline (10 mL/kg, intramuscularly). At 24 hours after the glycerol injection, rats were sacrificed by decapitation. Control rats were injected with normal saline. The protein expression of NHE3, NBC1 and Na(+),K(+)-ATPase α1 subunit was determined in the cortex of the kidney by immunoblotting and immunohistochemistry. Following the treatment of glycerol, creatinine clearance was significantly decreased, and high anion gap metabolic acidosis developed. In the experimental group, the expression of Na(+),K(+)-ATPase α1 subunit was significantly decreased in the cortex of the kidney. On the contrary, the expression of NHE3 and NBC1 was significantly increased. Immunohistochemical analyses confirmed the immunoblotting data. In conclusion, the coordinate up-regulation of NHE3 and NBC1 may play an adaptive role against the metabolic acidosis in glycerol-induced rhabdomyolysis.

Keywords: Metabolic acidosis; Rhabdomyolysis; Type 1 Na+/HCO3- cotransporter; Type 3 Na+/H+ exchanger.

Fig. 1

Hematoxylin and Eosin stained sections of kidneys. There is tubular cell necrosis, intraluminal casts, hemorrhagic casts, tubular obstruction, and tubular dilatation, swelling and flattening of proximal tubular cells with brush border loss in glycerol-treated kidneys while glomerular morphology remains unchanged. Magnification ×100.

Fig. 2

Expression of Na⁺,K⁺-ATPase α1 subunit in the cortex of the kidney. The protein expression of Na⁺,K⁺-ATPase α1 subunit was significantly decreased in the cortex of the kidney following the glycerol treatment. ^*p<0.05 vs control rats. Magnification ×100.

Fig. 3

Expression of type 3 Na⁺/H⁺ exchanger (NHE3) (A) and type 1 Na⁺/HCO₃^- cotransporter (NBC1) (B) in the cortex of the kidney. The protein expression of NHE3 and NBC1 was significantly increased following the glycerol treatment. ^*p<0.05 vs control rats.

Fig. 4

Immunoperoxidase microscopy of type 3 Na⁺/H⁺ exchanger (NHE3) and type 1 Na⁺/HCO₃^- cotransporter (NBC1) in the cortex of the kidney. Immunohistochemistry of NHE3 revealed apical membrane labeling of proximal tubule (PT) cells in the cortex, whereas the basolateral membranes were unlabeled. Consistent with the immunoblotting data, the NHE3 labeling was markedly increased after the glycerol treatment (A and B). Immunolabeling of NBC1 appeared in the basolateral plasma membrane of PT cells, which was also more prominent in the experimental group (C and D). Magnification ×400.