Ion exchange activity in pulmonary artery smooth muscle cells: the response to
hypoxia.
Madden, Jane A., Daniel E. Ray, Peter A. Keller, and Jack G. Kleinman.
Departments of 1Neurology and 3Medicine, The Medical College of Wisconsin, and
2Research Service, Zablocki Veterans Affairs Medical Center, Milwaukee, Wisconsin
53295
APStracts 7:0252L, 2000.
The purposes of this study were to determine 1) the presence of the major ion transport
activities that regulate cytoplasmic pH (pHc) in cat pulmonary artery smooth muscle
cells, i.e., Na+/H+ and the Na+-dependent and -independent Cl«minus»/«hco3»
exchange, 2) whether pHc changes in cells from small (SPAs) and large (LPAs)
pulmonary arteries during hypoxia, and 3) whether changes in pHc are due to changes in
the balance of exchange activities. Exchange activities as defined by physiological
maneuvers rather than molecular identity were ascertained with fluorescence microscopy
to document changes in the ratio of the pHc indicator 2'7'-bis-(2-carboxyethyl)-5-(and-6)-
carboxyfluorescein. Steady-state pHc was higher in LPA than in SPA normoxic smooth
muscle cells. SPAs and LPAs possessed all three transport activities; in «hco3»-
containing normoxic solutions, Cl«minus»/«hco3» exchange rather than Na+/H+
exchange set the level of pHc; in «hco3»-containing hypoxic solutions, pHc increased in
SPA and decreased in LPA cells; altering the baseline pHc of a cell type to that of the
other did not change the direction of the pHc response during hypoxia. The absence of
Na+ prevents hypoxia-induced alkalinization in SPA cells; in both cell types, inhibiting
the Cl«minus»/«hco3» exchange activities reversed the normal direction of pHc changes
during hypoxia.
Received 24 January 2000; accepted in final form 25 August 2000
APS Manuscript Number L0029-0.
Article publication pending Am J Physiol Lung Cell Mol Physiol
ISSN 1080-4757 Copyright 2000 The American Physiological Society.
Published in APStracts on 7 November 2000