Jung D W, Brierley G P
Department of Physiological Chemistry, Ohio State University, Columbus, Ohio 43210.
Plant Physiol. 1979 Dec;64(6):948-53. doi: 10.1104/pp.64.6.948.
Mitochondria isolated from potato tubers fail to undergo passive osmotic swelling when suspended in isotonic Na(+) acetate or phosphate, in NaCl following addition of tripropyltin, or in Na(+) nitrate following addition of an uncoupler. Swelling under each of these conditions in mitochondria from other sources has been attributed to the inward movement of Na(+) on an endogenous Na(+)/H(+) exchanger. Such a monovalent cation/H(+) exchanger has also been implicated in respiration-dependent cation extrusion and contraction of swollen mitochondria. Potato mitochondria swollen in chloride and nitrate salts extrude ions and contract when respiration is initiated. The contraction reaction is slower and less efficient than that in beef heart mitochondria, but like the latter, is sensitive to uncouplers and stimulated by nigericin, butacaine, and Mg(2+). These comparative studies suggest that a cation(+)/H(+) exchanger is present in potato tuber mitochondria, but that it functions exclusively as a cation-extruding mechanism. They further suggest that cation(+)/H(+) exchange activity is not identical in mitochondria from different sources and that these exchange components may have a directionality and regulatory features which differ with the metabolic needs of the source tissue.
从马铃薯块茎中分离出的线粒体，当悬浮于等渗的醋酸钠或磷酸盐溶液中、加入三丙基锡后的氯化钠溶液中或加入解偶联剂后的硝酸钠溶液中时，不会发生被动渗透肿胀。在其他来源的线粒体中，在上述每种条件下的肿胀都归因于内源性钠氢交换体上钠离子的向内移动。这种单价阳离子/氢离子交换体也与呼吸依赖性阳离子外排以及肿胀线粒体的收缩有关。在氯化物和硝酸盐盐溶液中肿胀的马铃薯线粒体在开始呼吸时会排出离子并收缩。收缩反应比牛心线粒体中的反应更慢且效率更低，但与后者一样，对解偶联剂敏感，并受到尼日利亚菌素、布他卡因和镁离子的刺激。这些比较研究表明，阳离子/氢离子交换体存在于马铃薯块茎线粒体中，但它仅作为一种阳离子外排机制发挥作用。它们进一步表明，不同来源线粒体中的阳离子/氢离子交换活性并不相同，并且这些交换成分可能具有与来源组织的代谢需求不同的方向性和调节特征。
