Premium
Regulation of Na + ‐K + ‐2Cl − cotransport in turkey red cells: the role of oxygen tension and protein phosphorylation
Author(s) -
Muzyamba M. C.,
Cossins A. R.,
Gibson J. S.
Publication year - 1999
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.1469-7793.1999.0421t.x
Subject(s) - cotransporter , chemistry , stimulation , staurosporine , biophysics , symporter , phosphorylation , biochemistry , sodium , endocrinology , protein kinase c , transporter , biology , organic chemistry , gene
1 Na + ‐K + ‐2Cl − cotransport (NKCC) was studied in turkey red cells using Na + dependence or bumetanide sensitivity of 86 Rb + influx to monitor activity of the transporter. 2 Deoxygenation was the major physiological stimulus for NKCC activity: oxygen tensions ( P O2 ) over the physiological range modulated the transporter, with a P O2 for half‐maximal activation of about 41 mmHg ( n = 3 ). In air, activity of NKCC was also stimulated by shrinkage and isoproteronol (isoprenaline, 5 μ m ). By contrast, in deoxygenated cells, although the transporter activity was markedly elevated, it was no longer sensitive to volume or β‐adrenergic stimulation. 3 Calyculin A, a protein phosphatase inhibitor, stimulated cotransport with a lag of about 5 min. N ‐Ethylmaleimide (NEM) inhibited cotransport and also blocked the stimulatory effect of calyculin A if administered before calyculin A. Stimulation by calyculin A and deoxygenation were not additive. Staurosporine (2 μ m ) inhibited deoxygenated‐stimulated K + influxes, but not those stimulated by calyculin A. NEM added during calyculin A stimulation, i.e. during the 5 min lag, caused transport activity to be clamped at levels intermediate between maximal (calyculin A alone) and control. Cells treated with calyculin A alone or with calyculin A followed by NEM were no longer sensitive to volume, isoproteronol or P O2 . 4 The results have characterized the interaction between deoxygenation and other stimuli of NKCC activity. They have also shown that it is possible to manipulate the transporter in a reciprocal way to that shown previously for K + ‐Cl − cotransport.