Hori R, Maegawa H, Okano T, Takano M, Inui K
J Pharmacol Exp Ther. 1987 Jun;241(3):1010-6.
Effect of sulfhydryl reagents on the transport of tetraethylammonium, an organic cation, has been studied in brush border membrane vesicles isolated from rat renal cortex. H+ gradient-dependent uptake of tetraethylammonium by the vesicles was inhibited by various sulfhydryl reagents in a dose-dependent manner, and the potency of the reagents was followed in the order of HgCl2 greater than p-chloromercuribenzoate, p-chloromercuribenzene sulfonate (PCMBS) greater than N-ethylmaleimide. In the absence of H+ gradient, tetraethylammonium uptake and efflux also were inhibited by p-chloromercuribenzoate and PCMBS. The sulfhydryl reagents did not affect the dissipation rate of H+ gradient across the membranes. Pretreatment of brush border membranes with PCMBS resulted in an inhibition of tetraethylammonium uptake in the presence and absence of H+ gradient, and this inhibition was reversed by subsequent treatment of the vesicles with thiols such as dithiothreitol, glutathione and cysteine. The inhibitory effect by PCMBS pretreatment was protected in the preincubation with unlabeled tetraethylammonium. These results suggest that sulfhydryl reagents inhibit the transport of tetraethylammonium by their specific interaction with the active sites of the carrier, and that sulfhydryl groups are essential for organic cation transport system in renal brush border membranes.
巯基试剂对有机阳离子四乙铵转运的影响已在从大鼠肾皮质分离的刷状缘膜囊泡中进行了研究。囊泡对四乙铵的H⁺梯度依赖性摄取受到各种巯基试剂的剂量依赖性抑制，试剂的效力顺序为HgCl₂ > 对氯汞苯甲酸 > 对氯汞苯磺酸盐（PCMBS）> N - 乙基马来酰亚胺。在没有H⁺梯度的情况下，对氯汞苯甲酸和PCMBS也抑制了四乙铵的摄取和流出。巯基试剂不影响跨膜H⁺梯度的消散速率。用PCMBS预处理刷状缘膜会导致在存在和不存在H⁺梯度的情况下四乙铵摄取受到抑制，随后用二硫苏糖醇、谷胱甘肽和半胱氨酸等硫醇处理囊泡可逆转这种抑制。PCMBS预处理的抑制作用在用未标记的四乙铵预孵育时受到保护。这些结果表明，巯基试剂通过与载体的活性位点特异性相互作用抑制四乙铵的转运，并且巯基对于肾刷状缘膜中的有机阳离子转运系统至关重要。
