Amiloride-sensitive Na+ transport in human red cells: Evidence for a Na/H exchange system |
| |
Authors: | Escobales Nelson Canessa Mitzy |
| |
Institution: | (1) Departments of Physiology and Biophysics, University of Puerto Rico, School of Medicine, 00936 San Juan, Puerto Rico;(2) Harvard Medical School, 02115 Boston, Massachusetts |
| |
Abstract: | Summary The role of transmembrane pH gradients on the ouabain, bumetanide and phloretin-resistant Na+ transport was studied in human red cells. Proton equilibration through the Jacobs-Stewart cycle was inhibited by the use of DIDS (125 m) and methazolamide (400 m). Red cells with different internal pH (pH
i
=6.4, 7.0 and 7.8) were prepared and Na+ influx was measured at different external pH (pH
o
=6.0, 7.0, 8.0). Na+ influx into acid-loaded cells (pH
i
=6.4) markedly increased when pH
o
was raised from 6.0 to 8.0. Amiloride, a well-known inhibitor of Na+/H+ exchange systems blocked about 60% of the H+-induced Na+ entry, while showing small inhibitory effects in the absence of pH gradients. When pH0 was kept at 8.0, the amiloride-sensitive Na+ entry was abolished as pH
i
was increased from 6.4 to 7.8. Moreover, measurements of H+ efflux into lightly buffered media indicated that the imposition of an inward Na+ gradient stimulated a net H+ efflux which was sensitive to the amiloride analog 5-N-methyl-N-butyl-amiloride. Furthermore, in the absence of a chemical gradient for Na+ (Na
i
+
=Na
0
+
=15mm,Em=+6.7 mV), an outward H+ gradient (pH
i
=6.4, pH0=8.0) promoted a net amiloride-sensitive Na+ uptake which was abolished at an external pH of 6.0. These findings are consistent with the presence of an amiloride-sensitive Na+/H+ exchange system in human red cells. |
| |
Keywords: | sodium transport amiloride Na+/H+ exchange erythrocytes |
本文献已被 SpringerLink 等数据库收录! |
|