Deuticke B, Lütkemeier P, Poser B
Institut für Physiologie, Medizinische Fakultät, RWTH Aachen, Germany.
Biochim Biophys Acta. 1992 Aug 10;1109(1):97-107. doi: 10.1016/0005-2736(92)90192-o.
Chemical and biophysical mechanisms underlying the thiol-dependent lytic action of tellurite (and selenite) on human erythrocytes were investigated using native and GSH-depleted cells. Exposure of GSH-depleted cells to tellurite alone produces oxidative cross-linking of membrane thiols paralleled by a moderate membrane leakiness comparable in its extent to that induced by other SH-oxidizing agents (diamide, periodate). Exposure to tellurite in presence of endogenous or exogenous GSH produces marked leakiness which stems from the formation of aqueous leaks permeant to ions and nonelectrolytes and sensitive to inhibition by phloretin. Apparent pore radii, derived from exclusion limits for polar non-electrolytes, range from 0.3 to at least 1.3 nm. Leak size increases with increasing exposure time and concentration of the modifier. Leak formation is paralleled by membrane rigidification based on the cross-linking of spectrin. Thiol-dependent leak formation by tellurite in GSH-depleted cells can be sustained not only by exogenous GSH but also by other thiols. Progress of leak formation by tellurite/thiol can not be reliably quenched by procedures such as removal of tellurite from the medium, inhibition of anion transport via band-3 protein, washing of the cells or low temperature. The reaction can, however, be terminated, even in the presence of tellurite, by addition of N-ethylmaleimide, presumably due to the blockage of thiols or thiol-analogous tellurium compounds. N-ethylmaleimide even brings about a partial reversal of leakiness, suggesting the contribution of a reversible and an irreversible component of tellurite damage. Membrane perturbation by tellurite/thiol involves the formation of a membrane permeant tellurium species, possibly HTe-, which is likely to induce progressive damage of membrane proteins by a redox shuttle going along with a formation of elemental tellurium and its reduction by thiols.
利用天然细胞和谷胱甘肽（GSH）耗竭的细胞，研究了亚碲酸盐（和亚硒酸盐）对人红细胞的硫醇依赖性裂解作用的化学和生物物理机制。将GSH耗竭的细胞单独暴露于亚碲酸盐会导致膜硫醇的氧化交联，同时伴有适度的膜渗漏，其程度与其他SH氧化剂（二酰胺、高碘酸盐）诱导的渗漏相当。在内源性或外源性GSH存在下暴露于亚碲酸盐会产生明显的渗漏，这是由于形成了对离子和非电解质通透且对根皮素抑制敏感的水性渗漏通道。根据极性非电解质的排除极限得出的表观孔半径范围为0.3至至少1.3纳米。渗漏大小随修饰剂暴露时间和浓度的增加而增加。渗漏的形成与基于血影蛋白交联的膜刚性化同时发生。亚碲酸盐在GSH耗竭的细胞中通过硫醇依赖性形成渗漏，不仅可以由外源性GSH维持，也可以由其他硫醇维持。亚碲酸盐/硫醇形成渗漏的过程不能通过诸如从培养基中去除亚碲酸盐、通过带3蛋白抑制阴离子转运、洗涤细胞或低温等程序可靠地淬灭。然而，即使在存在亚碲酸盐的情况下，通过添加N-乙基马来酰亚胺也可以终止反应，推测这是由于硫醇或硫醇类似的碲化合物被阻断。N-乙基马来酰亚胺甚至会使渗漏部分逆转，这表明亚碲酸盐损伤存在可逆和不可逆成分。亚碲酸盐/硫醇对膜的扰动涉及形成一种膜通透的碲物种，可能是HTe-，它可能通过与元素碲的形成以及硫醇对其还原相伴的氧化还原穿梭作用，诱导膜蛋白的渐进性损伤。
