| Autor: |
Putnam RW; Department of Physiology and Biophysics, Wright State University, School of Medicine, Dayton, Ohio 45435, USA., Douglas PB, Ritucci NA |
| Jazyk: |
angličtina |
| Zdroj: |
The American journal of physiology [Am J Physiol] 1996 Oct; Vol. 271 (4 Pt 1), pp. C1367-79. |
| DOI: |
10.1152/ajpcell.1996.271.4.C1367 |
| Abstrakt: |
The 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 Mg(2+)-ATPase activity, high ouabain and nitrendipine binding, and low Ca(2+)-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. |
| Databáze: |
MEDLINE |
| Externí odkaz: |
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