Perego C, Markovich D, Norbis F, Verri T, Sorribas V, Murer H
Institute of Physiology, University of Zürich, Switzerland.
Pflugers Arch. 1994 Jun;427(3-4):252-6. doi: 10.1007/BF00374531.
Small-intestinal sulphate absorption is a Na(+)-dependent process having its highest rate in the ileum; it involves brush-border membrane Na(+)-sulphate cotransport. Injection of rat ileal mRNA into Xenopus laevis oocytes induced Na(+)-dependent sulphate uptake in a dose-dependent manner, with no apparent effect on Na(+)-independent sulphate uptake. For mRNA-induced transport, the apparent Km value for sulphate interaction was 0.6 +/- 0.2 mM and that for sodium interaction was 25 +/- 2 mM (Hill coefficient: 2.3 +/- 0.3). mRNA-induced transport, was inhibited by thiosulphate, but not by phosphate or 4,4,'-diisothiocyanatostilbene-2,2'-disulphonic acid (DIDS). Using a rat renal Na(+)-sulphate cotransporter cDNA as a probe [NaSi-1; Markovich et al. (1993) Proc Natl Acad Sci USA 90:8073-8077], the highest hybridization signals (2.3 kb and 2.9 kb) were obtained in size fractions showing the highest expression of Na(+)-dependent sulphate transport in oocytes. Hybrid depletion experiments using antisense oligonucleotides (from the NaSi-1 cDNA sequence), provided further evidence that rat small-intestinal (ileal) Na(+)-sulphate cotransport is closely related to rat proximal-tubular brush-border membrane Na(+)-sulphate cotransport.
小肠硫酸盐吸收是一个依赖钠离子的过程，在回肠中速率最高；它涉及刷状缘膜钠离子-硫酸盐协同转运。将大鼠回肠mRNA注射到非洲爪蟾卵母细胞中，以剂量依赖的方式诱导了依赖钠离子的硫酸盐摄取，对不依赖钠离子的硫酸盐摄取没有明显影响。对于mRNA诱导的转运，硫酸盐相互作用的表观Km值为0.6±0.2 mM，钠离子相互作用的表观Km值为25±2 mM（希尔系数：2.3±0.3）。mRNA诱导的转运受到硫代硫酸盐的抑制，但不受磷酸盐或4,4'-二异硫氰酸根合芪-2,2'-二磺酸（DIDS）的抑制。使用大鼠肾钠离子-硫酸盐协同转运体cDNA作为探针[NaSi-1；Markovich等人（1993年）《美国国家科学院院刊》90:8073-8077]，在显示卵母细胞中依赖钠离子的硫酸盐转运最高表达的大小片段中获得了最高的杂交信号（2.3 kb和2.9 kb）。使用反义寡核苷酸（来自NaSi-1 cDNA序列）进行的杂交缺失实验，进一步证明了大鼠小肠（回肠）钠离子-硫酸盐协同转运与大鼠近端肾小管刷状缘膜钠离子-硫酸盐协同转运密切相关。
