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Desipramine Inhibits Na⁺/H⁺ Exchanger in Human Submandibular Cells

¹ Department of Physiology and
³ Department of Oral and Maxillofacial Surgery, School of Dentistry and Dental Research Institute, Seoul National University, Seoul 110-749, Korea; and
² Department of Physiology, Cheju National University College of Medicine, Jeju 690-756, Korea

View larger version (18K): [in a new window]   Figure 1. Desipramine inhibits intracellular pH recovery in acidified human submandibular acinar cells. (A) 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein (BCECF)-loaded dissociated human submandibular acinar cells were perfused with normal HCO3– buffers and then challenged with 15 mM NH4Cl (hatched bar) for acid loading. Thereafter, the bath solution was changed to a Na+-free HCO3–buffer (blank bar). After stabilization of the pH level, the intracellular pH recovery patterns were monitored in the absence or presence of 300 nM desipramine (filled bar). Typical pH traces from more than 10 separate experiments are presented. (B) Concentration-dependent effects of desipramine on pH recovery. Cells were treated with various concentrations of desipramine after acid-loading, and the rate of pH recovery was monitored. Each point was obtained from more than 3 separate experiments and is the mean ± SEM. The results were reproducible.

View larger version (25K): [in a new window]   Figure 2. Desipramine blocked pH recovery by the inhibition of Na+-dependent ion exchanger recovery in human submandibular acinar cells. (A) In HEPES buffer, the BCECF-loaded acinar cells were acid-loaded (hatched bar) and maintained in a Na+-free HEPES buffer (blank bar), and intracellular pH recovery patterns were monitored in the absence or presence of 3 µM (filled bar) desipramine and/or 5 µM 5-(N-ethyl-N-isopropyl)amiloride (EIPA, gray bar), a Na+/H+ exchanger inhibitor. (B) In HCO3– buffer, cells were acid-loaded (hatched bar) and maintained in a Na+-free HCO3– buffer (blank bar), and intracellular pH recovery patterns were monitored in the absence or presence of 3 µM (filled bar) desipramine and/or 500 µM 4,4'-diisothiocyanostilbene-2,2'-disulphonic acid (DIDS, gray bar), an Na+/HCO3– co-transporter inhibitor. Typical pH traces from more than 5 separate experiments are presented. (C) The effects of EIPA, DIDS, and desipramine on pH recovery. Cells were treated with 1 or 3 µM EIPA, 500 µM DIDS, and/or 3 µM desipramine (Desi) after the acid-loading, and the rates of pH recovery were monitored. Each point was obtained from more than 3 separate experiments and is the mean ± SEM. The results were reproducible. *P < 0.01 (compared with control).

View larger version (24K): [in a new window]   Figure 3. Desipramine blocked Na+-dependent ion-exchanger-mediated pH recovery in the human submandibular gland cell line, HSG cells. (A) In HCO3 – buffer, the BCECF-loaded HSG cells were acid-loaded (hatched bar) and maintained in a Na+-free HCO3– buffer (blank bar), and intracellular pH recovery patterns were monitored in the absence or presence of 3 µM (filled bar) desipramine and/or 5 µM EIPA (gray bar), an Na+/H+ exchanger inhibitor. (B) In HCO3 – buffer, HSG cells were acid-loaded (hatched bar) and maintained in a Na+-free HCO3 – buffer (blank bar), and intracellular pH recovery patterns were monitored in the absence or presence of 3 µM (filled bar) desipramine and/or 500 µM DIDS (gray bar), an Na+/HCO3– co-transporter inhibitor. Typical pH traces from more than 8 separate experiments are presented. (C) The effects of EIPA, DIDS, and desipramine on pH recovery. HSG cells were treated with 3 µM EIPA, 500 µM DIDS, and/or 3 µM desipramine (Desi) after the acid-loading, and the rates of pH recovery were monitored. Each point was obtained from more than 3 separate experiments and is the mean ± SEM. The results were reproducible. *P < 0.01 (compared with control).