Effect of phenazine methosulphate on K+ transport in human red cells

摘要

The effect of phenazine methosulphate ( PMS; 1 mM) on (Rb-86(+)) K+ transport in human red cells was investigated to ascertain its action on the K+-Cl-cotransporter (KCC; defined as the Cl- dependent component of K+ flux measured in the presence of ouabain and bumetanide) and the Ca2+- activated K+ channel (Gardos channel; defined as the clotrimazole, 5 muM, - sensitive K+ flux). In the presence of Ca2+, both transport pathways were stimulated but effects were markedly greater under deoxygenated conditions (5-fold for KCC; 20-fold for the Gardos channel). KCC activation was inhibited by prior treatment with calyculin A (100 nM), implying action via protein dephosphorylation. Activation of the Gardos channel correlated with 28 +/- 3% inhibition of the plasma membrane Ca2+ pump, with maximal activity reduced from 7.7 +/- 1.1 to 2.7 +/- 0.7 mumol.( l cells. h)(-1) ( all means +/- S. E. M. for n = 3), and a 3- fold increase in sensitivity of the channel to Ca2+ (EC50 reduced from 437 +/- 156 to 152 +/- 57 nM). Increased availability of NADH in deoxygenated conditions, resulting in increased free radical generation by PMS, may be responsible. We speculate that the similarity of the K+ transport phenotype produced by PMS to that seen in deoxygenated sickle cells is relevant to the pathophysiology of sickle cell disease. 8Copyright (C) 2003 S. Karger AG, Basel. [References: 36]