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Differential oxygen sensitivity of the K + ‐Cl − cotransporter in normal and sickle human red blood cells
Author(s) -
Gibson J. S.,
Speake P. F.,
Ellory J. C.
Publication year - 1998
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1111/j.1469-7793.1998.225bi.x
Subject(s) - cotransporter , bumetanide , chemistry , urea , ouabain , red blood cell , extracellular , ion transporter , furosemide , medicine , biochemistry , sodium , membrane , organic chemistry
1 K + influx and efflux were measured in normal (HbA) and sickle (HbS) red blood cells to investigate the interaction of swelling, H + ions and urea with O 2 (0 to 150 mmHg O 2 ) in the presence of ouabain and bumetanide (both 100 μM). 2 In HbA cells, K + ‐Cl − cotransport was O 2 dependent. At low oxygen tensions ( P O2 s) the transporter was inactive and refractory to low pH, swelling or urea. 3 Cl − ‐independent K + influxes in sickle cells were elevated at low P O2 s, as previously reported. Cl − ‐dependent K + influxes were large at both high and low P O2 s, whether stimulated by swelling, H + ions or urea. In the absence of O 2 , Cl − ‐dependent K + influxes were similar in magnitude to those measured at high P O2 s. The minimum for Cl − ‐dependent K + influx was observed at P O2 s of about 40‐70 mmHg. 4 K + efflux from HbS cells was stimulated by the addition of urea (500 mM). The rate constants were of similar magnitude whether measured at high P O2 or in the absence of O 2 , and were predominantly Cl − dependent under both conditions. 5 In HbS red blood cells, reduction of extracellular Ca 2+ , addition of 1 mM Mg 2+ or nitrendipine (10 μM) to the saline had no effect. Inhibitors of K + ‐Cl − cotransport, [(dihydroindenyl)oxy] alkanoic acid (DIOA; 100 μM) or calyculin A (0·1 μM), inhibited influxes by a similar magnitude to Cl − substitution. 6 Results are significant for the pathophysiology of sickle cell disease. Low pH and urea are able to stimulate KCl loss from sickle cells, leading to cellular dehydration, even in regions of low P O2 .