Effects of sodium and proton pump activity on respiratory burst and pH regulation of rat alveolar macrophages.
At pH 7.4, extracellular Na+ removal inhibited the rat alveolar macrophage respiratory burst (RB) stimulated by phorbol 12-myristate 13-acetate (PMA) or zymosan-activated serum (ZAS). At pH 6.8, the RB was lower and decreased the Na+ effect. Amiloride inhibited the ZAS RB independently of effects on Na(+)-H+ exchange, but did not affect PMA stimulation. NBD-Cl, an H(+)-ATPase inhibitor, significantly inhibited the PMA or ZAS RB. Na+ removal caused sustained elevation of intracellular free [Ca2+], which previous studies suggested inhibits the RB. Intracellular pH (pHi) was lower at pHo 6.8 compared with pHo 7.4, but not altered by Na+ removal. PMA stimulation resulted in acidification corresponding with onset of superoxide production. At pHo 7.4, recovery to baseline pHi occurred that was not inhibited by amiloride or Na+ removal. In contrast, amiloride slowed pHi recovery after an exogenous acid load. Addition of H(+)-ATPase inhibitors, NBD-Cl or bafilomycin, following PMA stimulation or acid loading, inhibited pHi restoration. These studies suggest that pHi regulation following stimulation was mainly through a proton pump, whereas Na(+)-H+ exchange occurred only after greater acid loading. Nevertheless, Na+ and pH interacted to modulate the RB independent of Na(+)-H+ exchange.
Murphy
J K
JK
Cell Biology Group of Childrens Hospital Los Angeles, California 90027.
Forman
H J
HJ
D009327:4-Chloro-7-nitrobenzofurazan / Q000494:pharmacology; D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D006706:Homeostasis; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D007700:Kinetics; D016676:Macrophages, Alveolar / Q000187:drug effects / Q000502:physiology*; D017494:Proton Pumps / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012964:Sodium / Q000494:pharmacology*; D000254:Sodium-Potassium-Exchanging ATPase / Q000502:physiology*; D013481:Superoxides / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013997:Time Factors; D015054:Zymosan / Q000494:pharmacology
D017494:Proton Pumps; D013481:Superoxides; D000584:Amiloride; D015054:Zymosan; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase; D009327:4-Chloro-7-nitrobenzofurazan; D013755:Tetradecanoylphorbol Acetate