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- Title
Cell shrinkage evoked by Ca<sup>2+</sup>-free solution in rat alveolar type II cells: Ca<sup>2+</sup> regulation of Na<sup>+</sup>-H<sup>+</sup> exchange.
- Authors
Murao, Hitoshi; Shimizu, Akira; Hosoi, Keita; Iwagaki, Akitaka; Min, Kyong-Yob; Kishima, Gen-ichi; Hanafusa, Toshiaki; Kubota, Takahiro; Kato, Masumi; Yoshida, Hideyo; Nakahari, Takashi
- Abstract
The effects of intracellular Ca2+ concentration, [Ca2+]i, on the volume of rat alveolar type II cells (AT-II cells) were examined. Perfusion with a Ca2+-free solution induced shrinkage of the AT-II cell volume in the absence or presence of amiloride (1 µM, an inhibitor of Na+ channels); however, it did not in the presence of 5-(N-methyl-N-isobutyl)-amiloride (MIA, an inhibitor of Na+-H+ exchange). MIA decreased the volume of AT-II cells. Inhibitors of Cl--HCO3- exchange, 4,4′-diisothiocyanostilbene-2,2′-disulfonic acid (DIDS) and 4-acetamido-4′-isothiocyanatostilbene-2,2′-disulfonic acid (SITS) also decreased the volume of AT-II cells. This indicates that the cell shrinkage induced by a Ca2+-free solution is caused by a decrease in NaCl influx via Na+-H+ exchange and Cl--HCO3- exchange. Addition of ionomycin (1 µM), in contrast, induced cell swelling when AT-II cells were pretreated with quinine and amiloride. This swelling of the AT-II cells is not detected in the presence of MIA. Intracellular pH(pHi) measurements demonstrated that the Ca2+-free solution or MIA decreases pHi, and that ionomycin increases it. Ionomycin stimulated the pHi recovery after an acid loading (NH4+ pulse method), which was not noted in MIA-treated AT-II cells. Ionomycin increased [Ca2+]i in fura-2-loaded AT-II cells. In conclusion, the Na+-H+ exchange activities of AT-II cells, which maintain the volume and pHi, are regulated by [Ca2+]i.
- Subjects
CALCIUM; CELLS; AMILORIDE; SALT; QUININE
- Publication
Experimental Physiology, 2005, Vol 90, Issue 2, p203
- ISSN
0958-0670
- Publication type
Article
- DOI
10.1113/expphysiol.2004.028837