Devlin D J, Mills J W, Smith R P
Department of Pharmacology and Toxicology, Dartmouth Medical School, Hanover, New Hampshire 03756.
Toxicol Appl Pharmacol. 1989 Feb;97(2):247-55. doi: 10.1016/0041-008x(89)90329-3.
A previously described histochemical technique was applied to the localization of rhodanese (thiosulfate sulfurtransferase, EC 2.8.1.1) activity in rat skeletal muscle and liver. The physiological function of rhodanese is controversial, but it and other sulfurtransferases can catalyze the conversion of cyanide to the much less toxic thiocyanate. The volume of distribution of cyanide in human and dog is said to correspond roughly to the blood volume. Because of this and other observations, it was hypothesized that sulfurtransferase activity associated with the vascular endothelium on smooth muscle layers of blood vessels might play a role in cyanide detoxification. However, little enzyme activity as identified histochemically was associated with those sites in comparison with others examined. As expected, high activity was found in the liver and moderately high levels were present in skeletal muscle. In muscles sectioned longitudinally, points of rhodanese staining occurred in linear arrays along the lengths of the muscle fiber corresponding to the location of mitochondria within the fiber. The original technique called for incubation of tissue sections with both thiosulfate and cyanide. When thiosulfate was omitted, staining for rhodanese activity was still clearly identifiable in both liver and muscle sections with cyanide alone. In muscle sections the inclusion of both thiosulfate and cyanide resulted in a preferential staining of type I fibers presumably because of their higher content of mitochondria. Thus, this technique is a potential alternative to the NADH dehydrogenase stain for distinguishing between type I and type II muscle fibers. Incubation of tissue sections with only thiosulfate produced results that did not appear to differ from those obtained when both substrates were omitted. From these observations it may be inferred that the endogenous pool of sulfane-sulfur available to sulfurtransferases is larger than any alleged endogenous pool of cyanide. Although sulfurtransferase activity in muscle appeared to be lower than that in liver, the total body muscle mass is greater than the liver mass. Thus, these results support other evidence that skeletal muscle may make a significant contribution to total cyanide biotransformation in the absence of exogenously added thiosulfate.
一种先前描述的组织化学技术被用于大鼠骨骼肌和肝脏中硫氰酸酶（硫代硫酸盐硫转移酶，EC 2.8.1.1）活性的定位。硫氰酸酶的生理功能存在争议，但它和其他硫转移酶可催化氰化物转化为毒性小得多的硫氰酸盐。据说氰化物在人和狗体内的分布容积大致与血容量相当。基于此及其他观察结果，有人推测与血管平滑肌层的血管内皮相关的硫转移酶活性可能在氰化物解毒中发挥作用。然而，与其他检查部位相比，通过组织化学鉴定出的这些部位的酶活性很低。正如预期的那样，在肝脏中发现了高活性，在骨骼肌中存在中等水平的活性。在纵向切片的肌肉中，硫氰酸酶染色点沿肌纤维长度呈线性排列，对应于纤维内线粒体的位置。原始技术要求用硫代硫酸盐和氰化物孵育组织切片。当省略硫代硫酸盐时，仅用氰化物仍可在肝脏和肌肉切片中清晰地识别出硫氰酸酶活性染色。在肌肉切片中，同时加入硫代硫酸盐和氰化物会导致I型纤维优先染色，可能是因为它们的线粒体含量较高。因此，该技术是用于区分I型和II型肌纤维的NADH脱氢酶染色的潜在替代方法。仅用硫代硫酸盐孵育组织切片产生的结果似乎与省略两种底物时获得的结果没有差异。从这些观察结果可以推断，硫转移酶可用的内源性次磺酸硫池大于任何所谓的内源性氰化物池。虽然肌肉中的硫转移酶活性似乎低于肝脏中的活性，但全身肌肉质量大于肝脏质量。因此，这些结果支持了其他证据，即在外源添加硫代硫酸盐不存在的情况下，骨骼肌可能对总氰化物生物转化做出重大贡献。
