Wu G
Biochemistry Section, National Institute for Minamata Disease, Minamata City, Kumamoto, Japan.
J Appl Toxicol. 1996 Mar-Apr;16(2):95-102. doi: 10.1002/(SICI)1099-1263(199603)16:2<95::AID-JAT332>3.0.CO;2-S.
Methylmercury cysteine (MeHg-cysteine) uptake by rat erythrocytes (RBC) was undertaken at 5 and 20 degrees C. The effects of several amino acids, their derivatives, ATP, Na+, Mg2+ and membrane potential on MeHg-cysteine uptake were examined. The results showed that MeHg-cysteine uptake was temperature-dependent, Na(+)-dependent at 20 degrees C, partly Na(+)-dependent at 5 degrees C and Mg(2+)-dependent at 5 and 20 degrees C. The membrane potential had a very slight effect on MeHg-cysteine uptake. N-Acetyl-L-cysteine (AC), alanine, beta-alanine, cysteine sulphinic acid (CSA), gamma-aminobutyric acid (GABA), D-phenylalanine, phenylalanine, serine and taurine inhibited MeHg-cysteine uptake at 5 degrees C. Tryptophan both stimulated and inhibited at different sampling times at 5 degrees C. Glycine and methionine had stimulation at 5 degrees C. Aspartic acid, isoleucine, leucine and tyrosine had no effect on MeHg-cysteine uptake. GABA, D-phenylalanine and tryptophan lost their effects at 20 degrees C. The effects of glycine and serine had reversed at 20 degrees C. The half-time of MeHg-cysteine uptake was ca. 0.57 h at 5 degrees C and 0.23 h at 20 degrees C. Several amino acids and their derivatives had an influence on the half-times of MeHg-cysteine uptake. The present study suggested that MeHg-cysteine uptake by rat RBC at lower temperature involved several overlapping transport systems; the greatest contribution was likely to be due to system ASC. Direct evidence for system L in MeHg-cysteine uptake was not obtained in the present study.
在5℃和20℃条件下对大鼠红细胞（RBC）摄取甲基汞半胱氨酸（MeHg-半胱氨酸）的情况进行了研究。考察了几种氨基酸及其衍生物、ATP、Na⁺、Mg²⁺和膜电位对MeHg-半胱氨酸摄取的影响。结果表明，MeHg-半胱氨酸的摄取具有温度依赖性，在20℃时依赖于Na⁺，在5℃时部分依赖于Na⁺，在5℃和20℃时均依赖于Mg²⁺。膜电位对MeHg-半胱氨酸的摄取影响非常小。N-乙酰-L-半胱氨酸（AC）、丙氨酸、β-丙氨酸、半胱氨酸亚磺酸（CSA）、γ-氨基丁酸（GABA）、D-苯丙氨酸、苯丙氨酸、丝氨酸和牛磺酸在5℃时抑制MeHg-半胱氨酸的摄取。色氨酸在5℃的不同取样时间既有刺激作用又有抑制作用。甘氨酸和蛋氨酸在5℃时有刺激作用。天冬氨酸、异亮氨酸、亮氨酸和酪氨酸对MeHg-半胱氨酸的摄取没有影响。GABA、D-苯丙氨酸和色氨酸在20℃时失去作用。甘氨酸和丝氨酸的作用在20℃时发生了逆转。MeHg-半胱氨酸摄取的半衰期在5℃时约为0.57小时，在20℃时约为0.23小时。几种氨基酸及其衍生物对MeHg-半胱氨酸摄取的半衰期有影响。本研究表明，大鼠红细胞在较低温度下摄取MeHg-半胱氨酸涉及多个重叠的转运系统；最大的贡献可能归因于系统ASC。在本研究中未获得系统L参与MeHg-半胱氨酸摄取的直接证据。
