Klemm A R, Pell K L, Anderson L M, Andrew C L, Lloyd J B
Division of Developmental Biology, Jefferson Medical College and Nemours Research Programs, Alfred I. duPont Hospital for Children, P. O. Box 269, Wilmington, DE 19899, USA.
Biochim Biophys Acta. 1998 Aug 14;1373(1):17-26. doi: 10.1016/s0005-2736(98)00082-0.
The permeability of rat liver lysosomes to some inorganic and aliphatic organic anions was investigated, using an osmotic-protection methodology. Lysosomes were incubated at 25 degreesC in 250 mOsm solutions of potassium salts of the anions, in the presence of valinomycin, and the latency of lysosomal hexosaminidase measured at intervals. Lysosomes suspended in 250 mM sucrose at 25 degreesC were stable for up to 4 h. When suspended in 250 mOsm solutions of potassium salts of inorganic acids, latency was lost at rates indicating anion permeance decreasing in the order thiocyanate, nitrate and iodide>bromide>chloride>sulfate. This rank order does not correspond with the anion selectivity of any known anion transporter, and is closer to that of the lyotropic series. Results with the potassium salts of aliphatic organic acids indicate little correlation between permeation and hydrocarbon chain length, although formate was more rapidly permeant than acetate and its higher homologs. By contrast, oxalate was less permeable than other dicarboxylic acids. The presence of one or more hydroxy groups decreased permeance. A correlation between permeance and the acid's lowest pKa suggested that penetration was due principally to the entry of the undissociated acid, but there is evidence that the (much more abundant) singly charged anionic form is also significantly permeant.
采用渗透保护方法，研究了大鼠肝脏溶酶体对某些无机和脂肪族有机阴离子的通透性。溶酶体在25℃下于阴离子钾盐的250 mOsm溶液中孵育，同时存在缬氨霉素，并定期测量溶酶体己糖胺酶的潜伏时间。在25℃下悬浮于250 mM蔗糖中的溶酶体在长达4小时内保持稳定。当悬浮于无机酸钾盐的250 mOsm溶液中时，潜伏时间以一定速率丧失，表明阴离子通透性按硫氰酸盐、硝酸盐和碘化物>溴化物>氯化物>硫酸盐的顺序降低。这个排序与任何已知阴离子转运体的阴离子选择性都不相符，且更接近感胶离子序。脂肪族有机酸钾盐的结果表明，通透性与烃链长度之间几乎没有相关性，尽管甲酸盐比乙酸盐及其高级同系物的渗透性更快。相比之下，草酸盐的渗透性低于其他二羧酸。一个或多个羟基的存在会降低通透性。通透性与酸的最低pKa之间的相关性表明，渗透主要是由于未离解酸的进入，但有证据表明（数量多得多的）单电荷阴离子形式也具有显著的通透性。
