Scherer N M, Deamer D W
J Free Radic Biol Med. 1986;2(4):249-54. doi: 10.1016/s0748-5514(86)80006-x.
Calcium permeability of sarcoplasmic reticulum (SR) microsomes was measured after aging or after exposure to peroxydisulfate or to sulfhydryl-binding agents. Under conditions where the Ca2+-ATPase was active, the maximum net release of Ca2+ was not significantly different between control and oxidized SR. However, when calcium uptake was prevented by EGTA or apyrase, the Ca2+ permeability of oxidized microsomes was 2 to 3 times greater than control of low (10(-9), 10(-7) M) but not high (10(-6) M) levels of external calcium. The observation that vesicles preincubated with 5 mM dithiothreitol loaded up to 3 times as much calcium and had a slightly lower calcium permeability coefficient than control vesicles suggested that sulfhydryl oxidation might modulate calcium flux. This hypothesis was tested by exposing to sulfhydryl-binding agents: silver, arsenite, and p-chloromercuriphenylsulfonic acid. Sulfhydryl-binding agents initiated a rapid release of calcium from microsomes, and release was halted by dithiothreitol. Inhibition of calcium transport could not entirely account for the apparent increase in permeability because the calcium permeability of SR treated with sulfhydryl-binding agents was 5 times greater than that of SR exposed to Ca2+-ATPase inhibitors. These results suggest that oxidation may increase the calcium permeability of SR by allowing calcium loss through a channel that can be gated by sulfhydryl oxidation.
在老化、暴露于过二硫酸盐或巯基结合剂后，测定了肌浆网（SR）微粒体的钙通透性。在Ca2+-ATP酶活跃的条件下，对照和氧化后的SR之间Ca2+的最大净释放量无显著差异。然而，当用乙二醇双四乙酸（EGTA）或腺苷三磷酸双磷酸酶（apyrase）阻止钙摄取时，在外部钙水平较低（10^(-9)、10^(-7)M）而非较高（10^(-6)M）时，氧化微粒体的Ca2+通透性比对照高2至3倍。用5 mM二硫苏糖醇预孵育的囊泡摄取的钙多达对照囊泡的3倍，且钙通透性系数略低于对照囊泡，这一观察结果表明巯基氧化可能调节钙通量。通过暴露于巯基结合剂：银、亚砷酸盐和对氯汞苯磺酸来验证这一假设。巯基结合剂引发了微粒体中钙的快速释放，二硫苏糖醇可使释放停止。钙转运的抑制并不能完全解释通透性的明显增加，因为用巯基结合剂处理的SR的钙通透性比暴露于Ca2+-ATP酶抑制剂的SR高5倍。这些结果表明，氧化可能通过允许钙通过一个可被巯基氧化门控的通道流失，从而增加SR的钙通透性。
