AJP - Lung Cellular and Molecular Physiology, Vol 264, Issue 5 448-L457, Copyright © 1993 by American Physiological Society

ARTICLES

pH-induced calcium transients in type II alveolar epithelial cells

G. D. Gerboth, R. M. Effros, R. J. Roman and E. R. Jacobs
Department of Medicine, Medical College of Wisconsin, Milwaukee 53226.

Although both intracellular pH (pHi) and intracellular Ca2+ concentration ([Ca2+]i) are highly regulated and have important metabolic effects in alveolar epithelial cells, little is known about the interrelationship between these two ions in alveolar epithelial cells. The present study examined changes in [pH]i and [Ca2+]i in isolated alveolar epithelial cells using the fluorescent dyes SNARF-1 and fura-2. Basal pHi values in freshly isolated and cultured alveolar epithelial cells were 7.27 and 7.24, respectively. Resting [Ca2+]i values in freshly isolated cells (53 +/- 5 nM) were lower than those in cultured type II cells (107 +/- 21 nM). pHi increased rapidly after addition of 25 mM NH4Cl in both cultured and freshly isolated cells and then decreased back toward baseline over the following 10 min. The rise in pHi was associated with a transient increase in [Ca2+]i. Resuspension of cells in an NH4Cl-free solution resulted in rapid intracellular acidification, which recovered over the subsequent 10 min. Removal of sodium or addition of 1 mM amiloride to the external solution slowed the rate of recovery from intracellular acidification, consistent with the participation of Na(+)-H+ exchanger in this process. In freshly isolated cells, [Ca2+]i increased following acidification and then decreased as the cells recovered from an acid load. In cultured cells, [Ca2+]i also increased following acidification but then remained elevated over the subsequent 10 min. The recovery of [Ca2+]i toward baseline values in fresh cells following acidification was dependent on the presence of external sodium. These data demonstrate that both increases and decreases in pHi of alveolar epithelial cells are associated with increases in [Ca2+]i and suggest that some of the metabolic effects of altering pHi may be secondary to increases in [Ca2+]i. The dependency of [Ca2+]i recovery following acidification on external sodium raises the possibility that freshly isolated type II cells have Na(+)-Ca2+ exchangers that contribute to the regulation of [Ca2+]i.

This article has been cited by other articles:

				R. Murphy, V. V. Cherny, D. Morgan, and T. E. DeCoursey Voltage-gated proton channels help regulate pHi in rat alveolar epithelium Am J Physiol Lung Cell Mol Physiol, February 1, 2005; 288(2): L398 - L408. [Abstract] [Full Text] [PDF]

				M. Griese, A. Baatz, J. Beck, and B. Deubzer Uptake of a natural surfactant and increased delivery of small organic anions into type II pneumocytes Am J Physiol Lung Cell Mol Physiol, July 1, 2001; 281(1): L144 - L154. [Abstract] [Full Text] [PDF]

				B. E. Isakson, W. H. Evans, and S. Boitano Intercellular Ca2+ signaling in alveolar epithelial cells through gap junctions and by extracellular ATP Am J Physiol Lung Cell Mol Physiol, February 1, 2001; 280(2): L221 - L228. [Abstract] [Full Text] [PDF]

				J. B. Gordon, T. R. Halla, C. D. Fike, and J. A. Madden Mediators of alkalosis-induced relaxation in pulmonary arteries from normoxic and chronically hypoxic piglets Am J Physiol Lung Cell Mol Physiol, January 1, 1999; 276(1): L155 - L163. [Abstract] [Full Text] [PDF]