Transport of sodium and urea in outer medullary descending vasa recta.
Transport of sodium and urea in outer medullary descending vasa recta.
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DOI：
10.1172/jci116948
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发表时间：
1994
期刊：
影响因子：
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通讯作者：
T. Pallone;J. Work;R. Myers;R. Jamison
中科院分区：
文献类型：
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作者：
T. Pallone;J. Work;R. Myers;R. Jamison
我们从大鼠血管束中解剖并灌注外髓直血管（OMVR）。钠（PNa）和尿素（Pu）的渗透性同时确定从内腔到浴流出的22 Na和[14 C]尿素。PNa和Pu也通过Munich-Wistar大鼠乳头尖端的下行（DVR）和上行直血管（AVR）的体内微灌注来测量。在一些OMVR中，PNa与零难以区分。OMVR中PNa的平均+/- SE（x 10（-5），cm/s）为76 +/- 9。OMVR中的钚总是很高（x 10（-5），cm/s），360 +/- 14。OMVR、PNa与Pu无相关性。内髓AVR和DVR的PNa分别为115 +/- 10和75 +/- 10，Pu分别为121 +/- 10和76 +/- 11。PNa和Pu在乳头状直血管中总是几乎相同且高度相关。向水浴和管腔中加入未标记的尿素或根皮素可可逆地抑制OMVR中[14 C]尿素的转运，为载体介导的转运提供了证据。这些数据表明，钠和尿素可能通过细胞旁途径穿过内髓直血管壁，而尿素也通过跨细胞途径穿过OMVR。电子显微镜检查7在体外灌注OMVR显示没有开窗，这些血管暴露于10 μ M钙离子载体A23187或1 nM血管紧张素II导致可逆收缩，表明在体外灌注OMVR DVR只。
We dissected and perfused outer medullary vasa recta (OMVR) from vascular bundles in the rat. Permeabilities of sodium (PNa) and urea (Pu) were simultaneously determined from the lumen-to-bath efflux of 22Na and [14C]urea. PNa and Pu were also measured by in vivo microperfusion of descending (DVR) and ascending vasa recta (AVR) at the papillary tip of Munich-Wistar rats. In some OMVR PNa was indistinguishable from zero. The mean +/- SE of PNa (x 10(-5), cm/s) in OMVR was 76 +/- 9. Pu in OMVR was always very high (x 10(-5), cm/s), 360 +/- 14. There was no correlation between OMVR PNa and Pu. Inner medullary AVR and DVR had PNa of 115 +/- 10 and 75 +/- 10, respectively, and Pu of 121 +/- 10 and 76 +/- 11, respectively. PNa and Pu in papillary vasa recta were always nearly identical and highly correlated. Transport of [14C] urea in OMVR was reversibly inhibited by addition of unlabeled urea or phloretin to the bath and lumen, providing evidence for carrier-mediated transport. These data suggest that sodium and urea might traverse the wall of inner medullary vasa recta by a paracellular pathway while urea also crosses by a transcellular route in OMVR. Electron microscopic examination of seven in vitro perfused OMVR revealed no fenestrations and exposure of these vessels to 10 microM calcium ionophore A23187 or 1 nM angiotensin II resulted in reversible contraction, suggesting that in vitro perfused OMVR are DVR only.