Intracellular pH regulation in isolated myocytes from adult rat heart in HCO3(-)-containing and HCO3(-)-free media.
1. Using microfluorimetry, intracellular pH, buffering capacity and intracellular pH recovery from intracellular acidosis were determined in isolated adult rat ventricular myocytes, in buffers with and without HCO3-. 2. In nominally HCO3(-)-free media, the intracellular pH was higher than in HCO3(-)-containing media. Buffering capacity at resting intracellular pH and at a pH of about 6.3 was also lower in HCO3(-)-free media. 3. In HCO3(-)-free media, recovery from an acid load after an NH4Cl prepulse was almost completely inhibited by the Na+/H+ antiport activity specific inhibitor ethylisopropyl amiloride. However, in the presence of HCO3-, H+ efflux rate was enhanced, and ethylisopropyl amiloride led to only partial inhibition of H+ efflux. Complete inhibition was achieved only with further addition of the anion-transport inhibitor 4,4'-di-isothiocyanatostilbene-2,2'-disulphonate. 4. Thus, in adult rat ventricular myocytes, recovery from intracellular acidosis in the absence of HCO3- was almost wholly due to Na+/H+ antiport activity. In the more physiological situation with HCO3- present, a third of the recovery from an intracellular acid load was attributed to an additional external Na(+)-dependent di-isothiocyanatostilbene-disulphonate-sensitive H+ efflux.
Department of Pharmacology, Leicester Royal Infirmary, U.K.
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Ng
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Davies
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Quinn
D000584:Amiloride / Q000031:analogs & derivatives / Q000378:metabolism; D000818:Animals; D001557:Benzenesulfonates / Q000378:metabolism; D001639:Bicarbonates / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism; D002478:Cells, Cultured / Q000737:chemistry; D005470:Fluorometry; D006863:Hydrogen-Ion Concentration; D007424:Intracellular Fluid / Q000378:metabolism*; D017879:Isothiocyanates; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D017923:Sodium-Hydrogen Exchangers; D013861:Thiocyanates / Q000378:metabolism
D001557:Benzenesulfonates; D001639:Bicarbonates; D002352:Carrier Proteins; D017879:Isothiocyanates; D017923:Sodium-Hydrogen Exchangers; D013861:Thiocyanates; C068272:2,5-diisothiocyanatobenzenesulfonate; D000584:Amiloride; C039614:ethylisopropylamiloride