Brunette M G, Dennis V W
Can J Physiol Pharmacol. 1982 Mar;60(3):276-81. doi: 10.1139/y82-038.
Several recent studies have suggested that the alkaline phosphatase situated in the brush border membrane of the proximal convoluted tubule is positively related to inorganic phosphate reabsorption through this segment of the nephron. We examined this hypothesis by studying the influence of an inhibitor of alkaline phosphatase, L-bromotetramisole, upon phosphate transport through the isolated rabbit tubule, phosphate transport through brush border membrane vesicles of rats, and phosphate efflux from these vesicles. Results were compared with those obtained with D-bromotetramisole which is inactive on alkaline phosphatase. The microperfusion studies on isolated tubules did not show any significant influence of L-bromotetramisole on phosphate transport which slightly increased by 0.22 +/- 0.78 pmol . mm-1 . min-1 (NS). The experiments performed on brush border membrane vesicles indicated that at pH 7.5, both L- and D-bromotetramisole at a concentration of 0.1 mM slightly but significantly increased phosphate input from 1800 +/- 149 to 1999 +/- 157 and 1982 +/- 168 pmol/mg protein per 30-S incubation (P less than 0.01 and P less than 0.005, respectively). At pH 8.5, the same tendency was observed but was significant with the D isomer only. Finally, the effect of an increasing phosphate transport was accentuated when both isomers were tested at 1.0-mM concentration. Phosphate efflux from brush border membrane vesicles was not influenced by L- or D-bromotetramisole at 0.1 mM. At 1.0 mM, however, both isomers accelerated this release. These results do not support the hypothesis of a direct action of alkaline phosphate upon phosphate transport through the entire proximal convoluted tubule, nor upon input or output of this electrolyte through the brush border membrane vesicles. The two forms of bromotetramisole have variable effects upon phosphate transport which are unrelated to the alkaline phosphatase activity.
最近的几项研究表明，位于近端肾小管刷状缘膜的碱性磷酸酶与通过该肾单位段的无机磷重吸收呈正相关。我们通过研究碱性磷酸酶抑制剂L-溴四咪唑对通过分离的兔肾小管的磷酸盐转运、通过大鼠刷状缘膜囊泡的磷酸盐转运以及这些囊泡的磷酸盐外排的影响，来检验这一假设。将结果与用对碱性磷酸酶无活性的D-溴四咪唑获得的结果进行比较。对分离肾小管的微量灌注研究未显示L-溴四咪唑对磷酸盐转运有任何显著影响，磷酸盐转运略有增加，增加了0.22±0.78 pmol·mm⁻¹·min⁻¹（无显著性差异）。在刷状缘膜囊泡上进行的实验表明，在pH 7.5时，浓度为0.1 mM的L-和D-溴四咪唑均使每30秒孵育的磷酸盐输入量从1800±149轻微但显著增加至1999±157和1982±168 pmol/mg蛋白质（分别为P＜0.01和P＜0.005）。在pH 8.5时，观察到相同趋势，但仅D-异构体显著。最后，当两种异构体在1.0 mM浓度下进行测试时，磷酸盐转运增加的效应更为明显。0.1 mM的L-或D-溴四咪唑对刷状缘膜囊泡的磷酸盐外排没有影响。然而，在1.0 mM时，两种异构体均加速了这种释放。这些结果不支持碱性磷酸酶对通过整个近端肾小管的磷酸盐转运、或通过刷状缘膜囊泡对该电解质的输入或输出有直接作用的假设。两种形式的溴四咪唑对磷酸盐转运有不同影响，这与碱性磷酸酶活性无关。
