Maril Nimrod, Margalit Raanan, Mispelter Joel, Degani Hadassa
Department of Biological Regulation, Weizmann Institute of Science, Rehovot 76100, Israel.
Magn Reson Med. 2005 Mar;53(3):545-52. doi: 10.1002/mrm.20359.
Renal function is highly correlated with the sodium concentration gradient along the corticomedullary axis. The application of 3D high-resolution sodium magnetic resonance imaging (MRI) provided a means to quantify in vivo the spatial and temporal changes in renal tissue sodium concentration under normal and diuretic conditions. A detailed, pixel-by-pixel analysis of the intact rat kidney sodium MR images yielded a quantitative measure of the corticomedullary sodium gradient before and at early and later times after the administration of two distinct diuretic agents, furosemide and mannitol. Furosemide, a loop diuretic, induced a fivefold reduction in the cortical-outer medullary sodium gradient, whereas mannitol, an osmotic diuretic, did not affect this gradient. Both diuretics induced a 50% decrease in the sodium concentration of the inner medulla; however, mannitol exerted its effect twice as fast as furosemide with a 2.5-min exponential decay constant. These specific changes were attributed to the different mechanism of action and site of activity of each diuretic agent. Thus, high-resolution (23)Na MRI offers a unique, noninvasive tool for functional imaging of the kidney physiology.
肾功能与沿皮质髓质轴的钠浓度梯度高度相关。三维高分辨率钠磁共振成像（MRI）的应用提供了一种手段，可在正常和利尿条件下对肾组织钠浓度的时空变化进行体内定量。对完整大鼠肾脏钠磁共振图像进行逐像素详细分析，得出了在给予两种不同利尿剂（呋塞米和甘露醇）之前、早期和晚期时皮质髓质钠梯度的定量测量结果。袢利尿剂呋塞米使皮质-外髓质钠梯度降低了五倍，而渗透性利尿剂甘露醇则不影响该梯度。两种利尿剂均使内髓质钠浓度降低了50%；然而，甘露醇起效速度是呋塞米的两倍，指数衰减常数为2.5分钟。这些特定变化归因于每种利尿剂不同的作用机制和活性部位。因此，高分辨率（23）Na MRI为肾脏生理学的功能成像提供了一种独特的非侵入性工具。
