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首页> 外文期刊>American Journal of Physiology >Calcium-sensing receptor regulation of PTH-inhibitable proximal tubule phosphate transport.
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Calcium-sensing receptor regulation of PTH-inhibitable proximal tubule phosphate transport.

机译：钙敏感受体调节PTH抑制近端小管磷酸盐转运。

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Inorganic phosphate (Pi) is absorbed by proximal tubules through a cellular pathway that is inhibited by parathyroid hormone (PTH). The calcium-sensing receptor (CaSR) is expressed on apical membranes of proximal tubules. In the present studies, we determined the effect of luminal and/or basolateral PTH on phosphate absorption and tested the hypothesis that CaSR activation blocks PTH-inhibitable phosphate absorption. Single proximal S3 tubules were dissected from the kidneys of mice and studied by the Burg technique. Tubules were bathed with DMEM culture media supplemented with 6% BSA and perfused with an ultrafiltrate prepared from the bathing solution. 33P and FITC-inulin were added to the luminal perfusate to measure phosphate absorption (JPi) and fluid absorption (Jv), respectively. JPi averaged 2.9 pmol.min-1.mm-1 under control conditions and decreased by 20% upon addition of serosal PTH. PTH had no effect on Jv. Inclusion of PTH in the luminal perfusate reduced JPi to 2.1 pmol. min-1. mm-1. Combined addition of PTH to perfusate and bathing solutions reduced JPi to 1.5 pmol. min-1. mm-1 without affecting Jv. Indirect immunofluorescence studies revealed abundant PTH receptor (PTH1R) expression on brush-border membranes, with lower amounts on basolateral membranes. CaSRs were localized primarily, but not exclusively, to brush-border membranes. CaSR activation with luminal Gd3+ abolished the inhibitory action of PTH on JPi. Addition of Gd3+ to the serosal bathing solution had no effect on PTH-sensitive JPi. Gd3+ i.e., PTH-independent JPi. Gd3+ did not affect basal, had no effect on Jv when added to lumen or bath. Dopamine-inhibitable JPi was not affected by Gd3+. Experiments with proximal-like opossum kidney cells showed that elevated extracellular Ca2+ or NPS R467, a type II calcimimetic, inhibited PTH action on Pi uptake. In conclusion, PTH1Rs are expressed on apical and basolateral membranes of mouse proximal tubules. Stimulating apical or basolateral PTH1R inhibits phosphate absorption. CaSR activation specifically regulates PTH-suppressible phosphate absorption.
机译：无机磷酸盐（Pi）通过甲状旁腺激素（PTH）抑制的细胞途径被近端小管吸收。钙敏感受体（CaSR）在近端小管的顶膜上表达。在本研究中，我们确定了腔内和/或基底外侧PTH对磷酸盐吸收的影响，并验证了CaSR激活阻止PTH抑制磷酸盐吸收的假设。从小鼠肾脏切开单个近端S3小管，并通过Burg技术进行研究。将小管用补充有6％BSA的DMEM培养基浸浴，并用从浸浴液中制备的超滤液进行灌注。将33P和FITC-菊粉分别添加到腔内灌注液中，以分别测量磷酸盐吸收（JPi）和液体吸收（Jv）。 JPi在对照条件下平均为2.9 pmol.min-1.mm-1，加入浆膜PTH后降低了20％。 PTH对合资公司没有影响。在腔内灌注液中加入PTH可将JPi降低至2.1 pmol。 min-1。毫米-1在灌注液和沐浴液中联合添加PTH可将JPi降至1.5 pmol。 min-1。 mm-1而不会影响合资企业。间接免疫荧光研究表明，刷状边界膜上有大量PTH受体（PTH1R）表达，而基底外侧膜上的PTH受体含量较低。 CaSRs主要但非唯一地局限于刷膜。 CaSR激活腔Gd3 +废除了PTH对JPi的抑制作用。在浆膜沐浴液中添加Gd3 +对PTH敏感的JPi没有影响。 Gd3 +，即独立于PTH的JPi。当添加到管腔或浴液中时，Gd3 +不影响基础，对Jv没有影响。多巴胺抑制性JPi不受Gd3 +的影响。用近端样负鼠肾细胞进行的实验表明，升高的细胞外Ca2 +或NPS R467（II型拟钙剂）抑制了PTH对Pi吸收的作用。总之，PTH1Rs在小鼠近端小管的顶膜和基底外侧膜上表达。刺激根尖或基底外侧的PTH1R抑制磷酸盐的吸收。 CaSR激活特别调节PTH可抑制的磷酸盐吸收。

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