N A Tobey1, G Koves, R C Orlando. 1. Department of Medicine, Tulane University School of Medicine, and the Veterans Administration Medical Center, New Orleans, Louisiana, USA.
Abstract
OBJECTIVE: The human esophagus is regularly exposed to refluxed gastric acid. Therefore, its epithelial cells require for survival a means of extruding excess H+ from the cytoplasm. Because Na+/H+ exchange activity has been observed in many mammalian cell types, including that of rabbit esophagus, we sought its presence in human esophageal epithelium. METHODS: Human esophageal epithelial cells derived from endoscopic biopsy specimens or surgical esophagectomy specimens were grown in primary culture and loaded with the fluorescent dye, 2'7'-bis(carboxyethyl)-5(6)-carboxyfluorescein, to monitor intracellular pH (pHi). RESULTS: Resting pHi in bicarbonate-free N'-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid was 7.5 +/- 0.03 (n = 50). Acidification using the NH4Cl prepulse technique lowered pHi by 0.6 +/- 0.02 pH units, with recovery ensuing at an initial rate of 0.09 +/- 0.04 pH units/min. Notably, the rate of recovery was faster the more acidic the pHi, and recovery was abolished by amiloride or replacement with an Na+-free buffer. Acidification by lowering pHo with HCl resulted in a similarly rapid rate of return as with the NH4Cl technique, and resting cells acidified by 0.17 +/- 0.02 pH units/5 min upon exposure to amiloride. CONCLUSIONS: Human esophageal cells possess an H+-extruding mechanism consistent with an Na+/H+ exchanger. This mechanism is active in resting cells, adapts to the degree of pHi lowering, and extrudes H+ efficiently whether loaded by intracellular or extracellular means, making it well suited for epithelial defense against acid injury.
OBJECTIVE: The human esophagus is regularly exposed to refluxed gastric acid. Therefore, its epithelial cells require for survival a means of extruding excess H+ from the cytoplasm. Because Na+/H+ exchange activity has been observed in many mammalian cell types, including that of rabbit esophagus, we sought its presence in human esophageal epithelium. METHODS:Human esophageal epithelial cells derived from endoscopic biopsy specimens or surgical esophagectomy specimens were grown in primary culture and loaded with the fluorescent dye, 2'7'-bis(carboxyethyl)-5(6)-carboxyfluorescein, to monitor intracellular pH (pHi). RESULTS: Resting pHi in bicarbonate-free N'-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid was 7.5 +/- 0.03 (n = 50). Acidification using the NH4Cl prepulse technique lowered pHi by 0.6 +/- 0.02 pH units, with recovery ensuing at an initial rate of 0.09 +/- 0.04 pH units/min. Notably, the rate of recovery was faster the more acidic the pHi, and recovery was abolished by amiloride or replacement with an Na+-free buffer. Acidification by lowering pHo with HCl resulted in a similarly rapid rate of return as with the NH4Cl technique, and resting cells acidified by 0.17 +/- 0.02 pH units/5 min upon exposure to amiloride. CONCLUSIONS:Human esophageal cells possess an H+-extruding mechanism consistent with an Na+/H+ exchanger. This mechanism is active in resting cells, adapts to the degree of pHi lowering, and extrudes H+ efficiently whether loaded by intracellular or extracellular means, making it well suited for epithelial defense against acid injury.
Authors: Andrew D Jones; Kathy D Bacon; Blair A Jobe; Brett C Sheppard; Clifford W Deveney; Michael J Rutten Journal: J Gastrointest Surg Date: 2003-01 Impact factor: 3.452
Authors: Xi Zhang; Edaire Cheng; Xiaofang Huo; Chunhua Yu; Qiuyang Zhang; Thai H Pham; David H Wang; Stuart J Spechler; Rhonda F Souza Journal: PLoS One Date: 2012-11-21 Impact factor: 3.240