Betaine transport in rabbit renal brush-border membrane vesicles.
Betaine transport in rabbit renal brush-border membrane vesicles.
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甜菜碱在兔肾刷状缘膜囊泡中的转运。
DOI：
10.1152/ajprenal.1993.264.6.f948
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发表时间：
1993
期刊：
影响因子：
--
通讯作者：
Wright,SH
中科院分区：
文献类型：
--
作者：
Wunz,TM;Wright,SH
从兔肾皮质分离的刷状缘膜囊泡（BBMV）的有机渗透压甜菜碱的运输的特点。无论是Na+或H+的间接梯度支持集中吸收的方式与平行的Na（+）-甜菜碱和H（+）-甜菜碱共转运过程的存在一致。集中吸收发生在单独的膜电位的存在下，表明甜菜碱运输是产电的。甜菜碱的积累不依赖于培养基中的氯化物。L-脯氨酸同时抑制甜菜碱转运的H（+）和Na（+）敏感组分，而甘氨酸则阻断H（+）敏感途径，对Na（+）敏感的甜菜碱转运影响不大。这两种途径都充分描述了米氏动力学。在Na（+）-梯度条件下在pH平衡条件下，总甜菜碱转运的最大速率（Jmax）= 50.8 +/- 13.3 nmol. mg-1.min-1，产生半最大吸收的总甜菜碱浓度（Kt）= 4.1 +/- 0.5 mM（无Na+），Jmax = 102.5 +/- 10.5 nmol.mg-1.min-1，Kt = 2.8 +/- 0.3 mM。施加Na+和H+梯度使Jmax（142 +/- 25.5 nmol.mg-1.min-1）显著高于单独Na+梯度的水平。我们的结论是，甜菜碱运输在肾脏BBMV涉及两个不同的运输途径，区分的基础上的敏感性，无论是Na+或H+和他们的特异性脯氨酸和甘氨酸。
Transport of the organic osmolyte betaine was characterized in brush-border membrane vesicles (BBMV) isolated from rabbit renal cortex. Inwardly directed gradients of either Na+ or H+ supported concentrative uptake in a manner consistent with the presence of parallel Na(+)-betaine and H(+)-betaine cotransport processes. Concentrative uptake occurred in the presence of membrane potential alone, indicating that betaine transport is electrogenic. Accumulation of betaine was not dependent on chloride in the medium. Whereas L-proline inhibited both the H(+)- and Na(+)-sensitive components of betaine transport, glycine blocked the H(+)-sensitive pathway and had little effect on Na(+)-sensitive betaine transport. Both pathways were adequately described by Michaelis-Menten kinetics. Under Na(+)-gradient conditions (pH equilibrium), the maximal rate of total betaine transport (Jmax) = 50.8 +/- 13.3 nmol.mg-1.min-1 and the concentration of total betaine producing half-maximal uptake (Kt) = 4.1 +/- 0.5 mM. Under H(+)-gradient conditions (Na+ free), Jmax = 102.5 +/- 10.5 nmol.mg-1.min-1 and Kt = 2.8 +/- 0.3 mM. Imposition of both Na+ and H+ gradients increased Jmax (142 +/- 25.5 nmol.mg-1.min-1) to a level significantly greater than that noted in the presence of a Na+ gradient alone. We conclude that betaine transport in renal BBMV involves two distinct transport pathways that are differentiated on the basis of sensitivity to either Na+ or H+ and by their specificity to proline and glycine.