PROXIMAL TUBULAR SECRETION OF ANGIOTENSIN-II IN RATS
PROXIMAL TUBULAR SECRETION OF ANGIOTENSIN-II IN RATS
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DOI：
10.1152/ajprenal.1993.264.5.f891
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发表时间：
1993-05-01
影响因子：
--
通讯作者：
NAVAR, LG
中科院分区：
文献类型：
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作者：
BRAAM, B;MITCHELL, KD;NAVAR, LG
现在已经确定，局部形成血管紧张素II（ANG II）所需的所有成分都共存于肾脏中，并可改变局部ANG II的产生速率。然而，有关肾脏内不同隔室中ANG II浓度的数据有限。最近，近端小管液ANG II浓度在纳摩尔范围内的报道。使用ANG II放射免疫分析程序与增强的灵敏度，我们进行了实验，以探讨近端肾小管液ANG II水平进一步，并确定ANG II的来源。总自由流动近端肾小管液样本（n = 11）的平均ANG II浓度为13 +/- 2 nM。这些浓度在收集到含有抑制剂依那普利拉和EDTA的移液管中的样品中相似（10 +/- 2 nM）（n = 17）。从阻塞的近端小管收集的液体用人工小管液灌注，在灌注液中存在（22 +/- 3 nM）和不存在（22 +/- 4 nM）血管紧张素转换酶抑制剂依那普利拉的情况下，显示出相似的ANG II浓度。血浆ANG II浓度要低得多，平均为155 +/- 26 pM。等渗盐水扩张使血浆ANG II水平降低至30 +/- 5 pM（P < 0.01），但没有显著降低腔内ANG II（8 +/- 1 nM）。这些数据提供了进一步的证据表明，肾小管内ANG II浓度在纳摩尔范围内，并独立于血浆ANG II水平进行调节。从灌注小管获得的数据表明，近端小管将大量ANG II或前体添加到管腔中。
It is now established that all of the components necessary for the local formation of angiotensin II (ANG II) coexist in the kidney and can alter local ANG II production rate. However, data on ANG II concentrations in different compartments within the kidney are limited. Recently, proximal tubule fluid ANG II concentrations in the nanomolar range were reported. Using an ANG II radioimmunoassay procedure with enhanced sensitivity, we performed experiments to explore proximal tubular fluid ANG II levels further and to determine the source of the ANG II. Total free-flow proximal tubular fluid samples (n = 11) had an average ANG II concentration of 13 +/- 2 nM. These concentrations were similar (10 +/- 2 nM) in samples collected into pipettes containing the inhibitors enalaprilat and EDTA (n = 17). Fluid collected from blocked proximal tubules that were perfused with artificial tubular fluid showed similar ANG II concentrations both in the presence (22 +/- 3 nM) and absence (22 +/- 4 nM) of the angiotensin-converting-enzyme inhibitor, enalaprilat, in the perfusate. Plasma ANG II concentrations were much lower and averaged 155 +/- 26 pM. Isotonic saline expansion lowered plasma ANG II levels to 30 +/- 5 pM (P < 0.01) but did not significantly decrease intraluminal ANG II (8 +/- 1 nM). These data provide further evidence that intratubular ANG II concentrations are in the nanomolar range and are regulated independently of the plasma ANG II levels. The data obtained from perfused tubules indicate that the proximal tubule adds substantial amounts of ANG II or a precursor into the tubular lumen.