Different mechanisms of adaptive increase in Na+-Pi cotransport across renal brush-border membrane.
Different mechanisms of adaptive increase in Na+-Pi cotransport across renal brush-border membrane.
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Na-Pi 跨肾刷状缘膜共转运适应性增加的不同机制。
DOI：
10.1152/ajprenal.1989.256.5.f852
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发表时间：
1989
期刊：
影响因子：
--
通讯作者：
Dousa,TP
中科院分区：
文献类型：
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作者：
Yusufi,AN;Szczepanska-Konkel,M;Hoppe,A;Dousa,TP
我们探讨了甲状腺激素（T3）和低磷饮食（LPD）引起肾刷状缘膜（BBM）Na+-Pi共转运适应性增加的生化机制。通过BBM囊泡（BBMV）对~（32）Pi的摄取测定Na ~+-Pi共转运速率，通过[14 C]膦甲酸（PFA）与BBMV的结合测定Na ~+-Pi共转运体的数量。在T3处理的大鼠和LPD喂养的大鼠的BBMV中，Na+梯度依赖性32 Pi摄取增加（Vmax增加; Km Pi不变）。T3处理后，BBMV上的Na+依赖性[14 C]PFA结合增加（Vmax更高，Km PFA无变化），但在喂食LPD的大鼠中保持不变。放线菌素D或放线菌酮可阻断Na+-Pi共转运和Na+依赖性[14 C]PFA结合对T3的反应。此外，苯甲醇BBMV在体外增加Na+-Pi的共运输，但[14 C]PFA结合没有改变，[3 H]根皮苷结合和其他溶质的共运输减少或没有改变。BBMV暴露于胆固醇降低Na+-Pi共转运，而不改变[14 C]PFA结合。我们认为，T3引起的Na+-Pi共转运的适应性增加是由于BBM中Na+-Pi共转运体数量的增加。与此相反，在响应LPD的Na+-Pi共转运体的数量是不变的，增加的Na+-Pi共转运是由于更快的Na+与Pi的易位，由于BBM的流动性增强。
We explored the biochemical mechanism by which thyroid hormone (T3) and low-phosphate diet (LPD) cause an adaptive increase in Na+-Pi cotransport across renal brush-border membrane (BBM). The rate of Na+-Pi cotransport was determined by 32Pi uptake by BBM vesicles (BBMV), and the number of Na+-Pi symporters was assessed by binding of [14C]phosphonoformic acid (PFA) on BBMV. In BBMV of both T3-treated rats and LPD-fed rats, the Na+ gradient-dependent 32Pi uptake increased (Vmax increased; Km Pi was not changed). The Na+-dependent [14C]PFA binding on BBMV increased (higher Vmax, no change in Km PFA) in response to T3, but it remained unchanged in rats fed LPD. Both the increase of Na+-Pi cotransport and of Na+-dependent [14C]PFA binding in response to T3 were blocked by actinomycin D or cycloheximide. Addition of benzyl alcohol to BBMV in vitro increased Na+-Pi cotransport, but [14C]PFA binding did not change; the [3H]phlorizin binding and cotransports of other solutes decreased or did not change. The exposure of BBMV to cholesterol decreased Na+-Pi cotransport without changing [14C]PFA binding. We suggest that the adaptive increase of Na+-Pi cotransport elicited by T3 is due to an increase in number of Na+-Pi cotransporters in BBM. In contrast, in response to LPD the number of Na+-Pi cotransporters is unchanged, and the increased Na+-Pi cotransport is due to faster translocation of Na+ with Pi due to enhanced fluidity of BBM.