The conductance of red blood cells from sickle cell patients: ion selectivity and inhibitors

• Published in: The Journal of physiology 2012-05, Vol.590 (9), p.2095-2105
• Main Authors: Ma, Y.‐L., Rees, D. C., Gibson, J. S., Ellory, J. C.
• Format: Article
• Language: English
• Subjects: 4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid - pharmacology; Anemia, Sickle Cell - blood; Benzaldehydes - pharmacology; Blood; Calcium - metabolism; Cardiovascular; Cell Membrane Permeability - drug effects; Dose-Response Relationship, Drug; Electric Conductivity; Erythrocyte Membrane - drug effects; Erythrocyte Membrane - metabolism; Hemoglobin, Sickle - metabolism; Humans; Hydrogen-Ion Concentration; Ion Transport; Magnesium - metabolism; Manganese - metabolism; Membrane Potentials; Membrane Transport Modulators - pharmacology; Oxygen - metabolism; Patch-Clamp Techniques; Pathogenesis; Peptides - pharmacology; Permeability; Potassium - metabolism; Protein Multimerization; Rubidium - metabolism; Sickle cell anemia; Sickle cell disease; Sodium - metabolism; Spider Venoms - pharmacology; Time Factors
• ISSN: 0022-3751; 1469-7793
• DOI: 10.1113/jphysiol.2012.229609

Key points  •  The high cation permeability in red blood cells (RBCs) from patients with sickle cell disease (SCD) is central to pathogenesis and includes a deoxygenation‐induced pathway termed Psickle. •  Here whole‐cell patch clamp configuration was used to record from RBCs of SCD patients and showed a conductance reversibly induced upon deoxygenation, permeable to univalent (Na+, K+, Rb+) and divalent (Ca2+, Mg2+) cations, and sensitive to tarantula spider toxin GsMTx‐4, Mn2+ and o‐vanillin. •  Divalent cation permeability is particularly important as entry of Ca2+ stimulates the Gardos channel whilst Mg2+ loss will stimulate KCl cotransport. •  In oxygenated RBCs, the conductance was pH sensitive, increasing as pH fell from 7.4 to 6, but unaffected when pH was raised from 7.4 to 8. •  Results show a conductance that shares many features with the Psickle flux pathway, and indicating its possible identity as a stretch‐activated channel with activation requiring sickle cell haemoglobin (HbS) polymerisation.   The abnormally high cation permeability in red blood cells (RBCs) from patients with sickle cell disease (SCD) occupies a central role in pathogenesis. Sickle RBC properties are notably heterogeneous, however, thus limiting conventional flux techniques that necessarily average out the behaviour of millions of cells. Here we use the whole‐cell patch configuration to characterise the permeability of single RBCs from patients with SCD in more detail. A non‐specific cation conductance was reversibly induced upon deoxygenation and was permeable to both univalent (Na+, K+, Rb+) and also divalent (Ca2+, Mg2+) cations. It was sensitive to the tarantula spider toxin GsMTx‐4. Mn2+ caused partial, reversible inhibition. The aromatic aldehyde o‐vanillin also irreversibly inhibited the deoxygenation‐induced conductance, partially at 1 mm and almost completely at 5 mm. Nifedipine, amiloride and ethylisopropylamiloride were ineffective. In oxygenated RBCs, the current was pH sensitive showing a marked increase as pH fell from 7.4 to 6, with no change apparent when pH was raised from 7.4 to 8. The effects of acidification and deoxygenation together were not additive. Many features of this deoxygenation‐induced conductance (non‐specificity for cations, permeability to Ca2+ and Mg2+, pH sensitivity, reversibility, partial inhibition by DIDS and Mn2+) are shared with the flux pathway sometimes referred to as Psickle. Sensitivity to GsMTx‐4 indicates its possible identi