SODIUM-DEPENDENT BICARBONATE ABSORPTION BY CORTICAL THICK ASCENDING LIMB OF RAT-KIDNEY
SODIUM-DEPENDENT BICARBONATE ABSORPTION BY CORTICAL THICK ASCENDING LIMB OF RAT-KIDNEY
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DOI：
10.1152/ajprenal.1985.248.6.f821
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发表时间：
1985-01-01
影响因子：
--
通讯作者：
GOOD, DW
中科院分区：
文献类型：
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作者：
GOOD, DW
采用离体微灌流实验研究了大鼠皮质厚段升支吸收碳酸氢盐的机制。以1.0-1.5 nl/min/mm灌注小管，灌注液和浴中碳酸氢盐浓度为25 mM。通过微量热法测定Bicycline吸收速率。对照组肾小管吸收碳酸氢盐的平均速率为9.5 ± 0.5。0.6极限管腔碳酸氢盐浓度为约pmol min/mm。对于在浴中用25 mM碳酸氢盐以缓慢速率灌注的小管，为5 mM。浴中的乙酰唑胺（10-4 M）使碳酸氢盐吸收减少76%，对跨上皮电压无显著影响。从灌注液和浴中去除Na或从浴中去除K将碳酸氢盐吸收和跨上皮电压降低至接近零。加入阿米洛利（5 × 10 - 6），10-4或10-3 M）使碳酸氢盐吸收减少60-75%，而对跨上皮电压没有可检测的影响。在灌注液中加入呋塞米（10-4 M）可使碳酸氢盐吸收显著增加40-50%，同时使跨上皮电压从17-1.8 mV降低。因此，皮质厚的上升肢的碳酸氢盐吸收需要碳酸酐酶活性和钠转运，但不依赖于跨上皮电压。Bicycline的吸收显然是由顶端膜Na-H交换介导的。
In vitro microperfusion experiments were performed to investigate the mechanism of bicarbonate absorption in the cortical thick ascending limb of the rat. Tubules were perfused at 1.0-1.5 nl/min/mm and bicarbonate concentration was 25 mM in the perfusate and bath. Bicarbonate absorption rates were determined by microcalorimetry. Control tubules absorbed bicarbonate at a mean rate of 9.5 .+-. 0.6 pmol min/mm. The limiting luminal bicarbonate concentration was .apprx. 5 mM for tubules perfused at slow rates with 25 mM bicarbonate in the bath. Acetazolamide (10-4 M) in the bath reduced bicarbonate absorption by 76% without significant effect on transepithelial voltage. Removing Na from the perfusate and bath or removing K from the bath reduced bicarbonate absorption and transepithelial voltage to near zero. Adding amiloride (5 .times. 10-4 or 10-3 M) to the perfusate reduced bicarbonate absorption by 60-75% without detectable effect on transepithelial voltage. Adding furosemide (10-4 M) to the perfusate increased bicarbonate absorption significantly by 40-50% while decreasing transepithelial voltage from 17-1.8 mV. Thus, bicarbonate absorption by cortical thick ascending limbs requires carbonic anhydrase activity and Na transport but is not dependent on transepithelial voltage. Bicarbonate absorption is evidently mediated by apical membrane Na-H exchange.