Fig. 7.

Response of acid-base transporters [Na⁺/H⁺ exchanger 3 (NHE3) and electrogenic basolateral Na⁺-${\text{HCO}}_3^{-}$ cotransporter (NBCe1)] and phosphate transporter (NaPi-IIa) to acetazolamide (ACTZ) or NH₄Cl loading for 2 wk. A and C: membrane fractions were isolated from the kidney cortex of rats treated with NH₄Cl loading (A) or ACTZ (C) versus their respective control or vehicle treatment and were used for immunoblot analysis using specific antibodies for each protein. B and D: corresponding average means ± SE of the densitometry analysis of transport proteins in response to NH₄Cl loading versus control (B) or in ACTZ-treated versus vehicle-treated rats (D). The abundance of these proteins was normalized to actin used for the control of gel loading. As shown, 2 wk of ACTZ caused a sharp downregulation of both NHE3 and NBCe1 but increased the abundance of NaPi-IIa. Except for NHE3, similar findings were seen in NH₄Cl-loaded rats with normal acid-base status. n = 5 rats in each group. Each lane was loaded with 40 μg protein from the kidney cortex. NS, not significant.