Wu G
Biochemical Section, National Institute for Minamata Disease, Kumamoto, Japan.
J Appl Toxicol. 1996 Jan-Feb;16(1):77-83. doi: 10.1002/(SICI)1099-1263(199601)16:1<77::AID-JAT319>3.0.CO;2-C.
The present study is a continuation of our experiments on methylmercury-cysteine (MeHg-cysteine) uptake by rat red blood cells (RBCs) at low temperature. Methylmercury-cysteine uptake by rat RBCs was conducted at 5 degrees C and 20 degrees C. The effects of Ca2+, colchicine, cytochalasin B, 4,4'-diisothiocyano-2,2'-stilbenedisulphonic acid (DIDS), N-ethylmaleimide (NEM), D-glucose, hexanol, L-homocysteine, ouabain, probenecid, sodium fluoride (NaF), vinblastine, and anisotonic changes on MeHg-cysteine uptake were examined. The results showed that MeHg-cysteine uptake at 5 degrees C could be described by Michaelis-Menten kinetics (v = VmaxS/(S+Km), where Km = 37.02 mM and Vmax = 320.84 mmol l-1 RBCs h-1), but MeHg-cysteine uptake at 20 degrees C could be described by Michaelis-Menten kinetics with a linear component (v = [VmaxS/(S + Km)] + KdS, where Km = 2.71 mM, Vmax = 250.72 mmol l-1 RBCs h-1, and Kd = 5.63 mM). Methylmercury-cysteine uptake was inhibited by colchicine, cytochalasin B, D-glucose, hexanol, NaF, NEM, ouabain, probenecid, vinblastine and 230 mosM hypotonicity but stimulated by Ca2+, DIDS, L-homocysteine and 460 mosM hypertonicity. The results in the present study suggest that MeHg-cysteine uptake by rat RBCs might be involved in the following three transport systems: an energy transport system sensitive to Ca2+, ouabain and NaF and subjected to Michaelis-Menten kinetics; an organic anion transport system sensitive to probenecid; and a facilitated diffusive transport for D-glucose sensitive to cytochalasin B. It is likely that most of the transport systems work at temperatures higher than 5 degrees C.
本研究是我们关于大鼠红细胞（RBCs）在低温下摄取甲基汞 - 半胱氨酸（MeHg - 半胱氨酸）实验的延续。大鼠红细胞摄取甲基汞 - 半胱氨酸的实验在5℃和20℃下进行。研究了Ca2 +、秋水仙碱、细胞松弛素B、4,4'-二异硫氰基 - 2,2'-二苯乙烯二磺酸（DIDS）、N - 乙基马来酰亚胺（NEM）、D - 葡萄糖、己醇、L - 同型半胱氨酸、哇巴因、丙磺舒、氟化钠（NaF）、长春花碱以及渗透压变化对MeHg - 半胱氨酸摄取的影响。结果表明，5℃下MeHg - 半胱氨酸的摄取可用米氏动力学描述（v = VmaxS/(S + Km)，其中Km = 37.02 mM，Vmax = 320.84 mmol l-1 RBCs h-1），但20℃下MeHg - 半胱氨酸的摄取可用带有线性成分的米氏动力学描述（v = [VmaxS/(S + Km)] + KdS，其中Km = 2.71 mM，Vmax = 250.72 mmol l-1 RBCs h-1，Kd = 5.63 mM）。秋水仙碱、细胞松弛素B、D - 葡萄糖、己醇、NaF、NEM、哇巴因、丙磺舒、长春花碱以及230 mosM的低渗环境可抑制甲基汞 - 半胱氨酸的摄取，但Ca2 +、DIDS、L - 同型半胱氨酸以及460 mosM的高渗环境可刺激其摄取。本研究结果表明，大鼠红细胞摄取MeHg - 半胱氨酸可能涉及以下三种转运系统：一种对Ca2 +、哇巴因和NaF敏感且符合米氏动力学的能量转运系统；一种对丙磺舒敏感的有机阴离子转运系统；以及一种对细胞松弛素B敏感的D - 葡萄糖易化扩散转运系统。很可能大多数转运系统在高于5℃的温度下起作用。
