ACELL September 46/3
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چکیده
Bonanno, Joseph A., Yi Guan, Sergey Jelamskii, and Xiao Jun Kang. Apical and basolateral CO2-HCO3 2 permeability in cultured bovine corneal endothelial cells. Am. J. Physiol. 277 (Cell Physiol. 46): C545–C553, 1999.—Corneal endothelial function is dependent on HCO3 2 transport. However, the relative HCO3 2 permeabilities of the apical and basolateral membranes are unknown. Using changes in intracellular pH secondary to removing CO2-HCO3 2 (at constant pH) or removing HCO3 2 alone (at constant CO2) from apical or basolateral compartments, we determined the relative apical and basolateral HCO3 2 permeabilities and their dependencies on Na1 and Cl2. Removal of CO2-HCO3 2 from the apical side caused a steady-state alkalinization (10.08 pH units), and removal from the basolateral side caused an acidification (20.05 pH units). Removal of HCO3 2 at constant CO2 indicated that the basolateral HCO3 2 fluxes were about three to four times the apical fluxes. Reducing perfusate Na1 concentration to 10 mM had no effect on apical flux but slowed basolateral HCO3 2 flux by one-half. In the absence of Cl2, there was an apparent increase in apical HCO3 2 flux under constant-pH conditions; however, no net change could be measured under constant-CO2 conditions. Basolateral flux was slowed ,30% in the absence of Cl2, but the net flux was unchanged. The steady-state alkalinization after removal of CO2-HCO3 2 apically suggests that CO2 diffusion may contribute to apical HCO3 2 flux through the action of a membraneassociated carbonic anhydrase. Indeed, apical CO2 fluxes were inhibited by the extracellular carbonic anhydrase inhibitor benzolamide and partially restored by exogenous carbonic anhydrase. The presence of membrane-bound carbonic anhydrase (CAIV) was confirmed by immunoblotting. We conclude that the Na1-dependent basolateral HCO3 2 permeability is consistent with Na-nHCO3 2 cotransport. Changes in HCO3 2
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ACELL September 46/3
Dodd, J. S., J. A. Raleigh, and T. S. Gross. Osteocyte hypoxia: a novel mechanotransduction pathway. Am. J. Physiol. 277 (Cell Physiol. 46): C598–C602, 1999.—Bone is a unique tissue in which to examine mechanotransduction due to its essential role in weight bearing. Within bone, the osteocyte is an ideal cellular mechanotransducer candidate. Because osteocytes reside distant from the blood supp...
متن کاملACELL September 46/3
Zeiske, Wolfgang, Ilse Smets, Marcel Ameloot, Paul Steels, and Willy Van Driessche. Intracellular pH shifts in cultured kidney (A6) cells: effects on apical Na1 transport. Am. J. Physiol. 277 (Cell Physiol. 46): C469–C479, 1999.—We report, for the epithelial Na1 channel (ENaC) in A6 cells, the modulation by cell pH (pHc) of the transepithelial Na1 current (INa), the current through the individu...
متن کاملACELL September 46/3
Shepard, Allan R., and James L. Rae. Electrically silent potassium channel subunits from human lens epithelium. Am. J. Physiol. 277 (Cell Physiol. 46): C412–C424, 1999.—We describe the cloning and characterization of the first human members, hKv9.1 and hKv9.3, of the electrically silent delayed-rectifying-like K1 channel subfamily. Their modulatory effects on the electrically active subfamily m...
متن کاملACELL September 46/3
Stevens, Randel J., Jeffery S. Weinert, and Nelson G. Publicover. Visualization of origins and propagation of excitation in canine gastric smooth muscle. Am. J. Physiol. 277 (Cell Physiol. 46): C448–C460, 1999.—The origin and spread of excitation were visualized with fluo 3 fluorescence in tissues isolated from canine gastric antrum. Sheets of circular muscle (5 3 6 mm) had at least 1 (30%) and...
متن کاملACELL August 46/2
JOHN M. PARK,1 ROSALYN M. ADAM,1 CRAIG A. PETERS,1 PAUL D. GUTHRIE,1 ZIJIE SUN,2 MICHAEL KLAGSBRUN,3 AND MICHAEL R. FREEMAN3 1Urologic Laboratory, Department of Urology, 3Laboratory for Surgical Research, Children’s Hospital, and Department of Surgery, Harvard Medical School, Boston, Massachusetts 02115; and 2Departments of Surgery and Genetics, Stanford University School of Medicine, Stanford,...
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