Joiner C H, Jiang M, Claussen W J, Roszell N J, Yasin Z, Franco R S
Cincinnati Comprehensive Sickle Cell Center, Children's Hospital Medical Center, 3333 Burnet Ave., Cincinnati, OH 45229-3039, USA.
Blood. 2001 Jun 15;97(12):3976-83. doi: 10.1182/blood.v97.12.3976.
Sickling-induced cation fluxes contribute to cellular dehydration of sickle red blood cells (SS RBCs), which in turn potentiates sickling. This study examined the inhibition by dipyridamole of the sickling-induced fluxes of Na(+), K(+), and Ca(++) in vitro. At 2% hematocrit, 10 microM dipyridamole inhibited 65% of the increase in net fluxes of Na(+) and K(+) produced by deoxygenation of SS RBCs. Sickle-induced Ca(++) influx, assayed as (45)Ca(++) uptake in quin-2-loaded SS RBCs, was also partially blocked by dipyridamole, with a dose response similar to that of Na(+) and K(+) fluxes. In addition, dipyridamole inhibited the Ca(++)-activated K(+) flux (via the Gardos pathway) in SS RBCs, measured as net K(+) efflux in oxygenated cells exposed to ionophore A23187 in the presence of external Ca(++), but this effect resulted from reduced anion conductance, rather than from a direct effect on the K(+) channel. The degree of inhibition of sickling-induced fluxes was dependent on hematocrit, and up to 30% of dipyridamole was bound to RBC membranes at 2% hematocrit. RBC membrane content of dipyridamole was measured fluorometrically and correlated with sickling-induced flux inhibition at various concentrations of drug. Membrane drug content in patients taking dipyridamole for other clinical indications was similar to that producing inhibition of sickling-induced fluxes in vitro. These data suggest that dipyridamole might inhibit sickling-induced fluxes of Na(+), K(+), and Ca(++) in vivo and therefore have potential as a pharmacological agent to reduce SS RBC dehydration. (Blood. 2001;97:3976-3983)
镰变诱导的阳离子通量导致镰状红细胞（SS RBCs）的细胞脱水，进而增强镰变。本研究检测了双嘧达莫在体外对镰变诱导的Na⁺、K⁺和Ca²⁺通量的抑制作用。在血细胞比容为2%时，10 μM双嘧达莫抑制了SS RBCs脱氧产生的Na⁺和K⁺净通量增加的65%。镰变诱导的Ca²⁺内流，以喹啉-2负载的SS RBCs中⁴⁵Ca²⁺摄取量测定，也被双嘧达莫部分阻断，剂量反应与Na⁺和K⁺通量相似。此外，双嘧达莫抑制了SS RBCs中Ca²⁺激活的K⁺通量（通过加尔多斯途径），在外部Ca²⁺存在下，以暴露于离子载体A23187的氧合细胞中的K⁺净外流来测量，但这种作用是由于阴离子电导降低，而不是对K⁺通道的直接作用。镰变诱导通量的抑制程度取决于血细胞比容，在血细胞比容为2%时，高达30%的双嘧达莫与RBC膜结合。通过荧光法测量RBC膜中双嘧达莫的含量，并将其与不同药物浓度下镰变诱导通量抑制相关联。因其他临床指征服用双嘧达莫的患者的膜药物含量与体外产生镰变诱导通量抑制的含量相似。这些数据表明双嘧达莫可能在体内抑制镰变诱导的Na⁺、K⁺和Ca²⁺通量，因此有潜力作为一种减少SS RBC脱水的药物。（《血液》。
