Membrane Domain Localization of pH-Regulating Transporters in Frog Skeletal Muscle Membrane VesiclesAmerican Journal of Physiology - Cell Physiology
AbstractThe distribution of pH-regulating transporters in surface and transverse (T) tubular membrane (TTM) domains of frog skeletal muscle was studied. 2',7'-Bis(carboxyethyl)-5(6)- carboxyfluorescein-loaded giant sarcolemmal vesicles, containing surface membrane, exhibited reversible Na+/H+ exchange. A microsomal vesicle fraction was shown to be enriched in TTM on the basis of high Na+-K+-ATPase and Mg2+-ATPase activity, high ouabain and nitrendipine binding, and low Ca2+-ATPase activity. TTM vesicles were well sealed and oriented inside out. Vesicles were loaded with the pH-sensitive dye pyranine. In response to an inwardly directed Na+ gradient, vesicles displayed virtually no alkalinization unless monensin was present. No pH response to an imposed Na+ gradient was seen regardless of the direction of the pH gradient across the vesicles, after phosphorylation of the vesicles with protein kinase C, or when exposed to guanosine 5'-O-(3-thiotriphosphate). In the presence of CO2, addition of Na+ or Cl- had no effect on vesicle pH. These data indicate that the TTM lacks functional pH-regulating transporters [Na+/H+ and (Na+ + HCO3-)/Cl- exchangers], suggesting that pH-regulating transporters are localized only to the surface membrane domain in frog muscle.
Citation InformationRobert W. Putnam, Phyllis B. Douglas and Nick A. Ritucci. "Membrane Domain Localization of pH-Regulating Transporters in Frog Skeletal Muscle Membrane Vesicles" American Journal of Physiology - Cell Physiology Vol. 271 Iss. 4 (1996) p. C1367 - C1379 ISSN: 0363-6143
Available at: http://works.bepress.com/robert_putnam/107/