Morgunov N S, Hirsch D J, Mobbs I G
Department of Physiology, Dalhousie University, Faculty of Medicine, Halifax, Nova Scotia, Canada.
Am J Physiol. 1989 Feb;256(2 Pt 2):F229-38. doi: 10.1152/ajprenal.1989.256.2.F229.
The urodele Ambystoma tigrinum adapts to a distilled water environment by decreasing renal sodium excretion, but the site and mechanism of renal adaptation is unknown. Isolated diluting segments of Ambystoma kidney were studied after a 2-wk exposure of the animals to either distilled or artificial pond ([Na] = 1.2 meq/l) water. Identification of diluting segments was confirmed by electron microscopy. Morphometric study revealed evidence of increased tubular diameter and cellular hypertrophy in the distilled water group. Na+-K+-ATPase activity was increased in tubules from the distilled water group compared with tubules from the pond water group; 40.2 +/- 6.9 vs. 21.7 +/- 4.3 nM ADP generated.min-1.mm tubule length-1, P less than 0.036. This alteration in ATPase activity was due to an increase in the number of pump units present on the basolateral membrane, since specific ouabain binding was also doubled in distilled water compound with pond water group tubules, 20.7 +/- 2.3 vs. 9.1 +/- 0.9 fmol/mm tubule length tubules, P less than 0.011. An increase in transepithelial potential difference of the diluting segment was noted in distilled water group tubules (19.5 +/- 1.4 mV) compared with tubules in the pond water group (13.2 +/- 1.8 mV), P less than 0.015. We conclude that distilled water adaptation is associated with specific diluting segment structural and functional alterations, which are probably linked to an increase in sodium transport rate.
虎纹钝口螈通过减少肾脏排钠来适应蒸馏水环境，但其肾脏适应的部位和机制尚不清楚。在将动物暴露于蒸馏水或人工池塘水（[Na]=1.2 毫当量/升）两周后，对虎纹钝口螈肾脏的分离稀释段进行了研究。通过电子显微镜确认了稀释段的鉴定。形态计量学研究显示，蒸馏水组存在肾小管直径增加和细胞肥大的证据。与池塘水组的肾小管相比，蒸馏水组肾小管中的 Na+-K+-ATP 酶活性增加；产生的 ADP 为 40.2±6.9 与 21.7±4.3 纳摩尔·分钟-1·毫米肾小管长度-1，P<0.036。ATP 酶活性的这种改变是由于基底外侧膜上泵单位数量的增加，因为在蒸馏水组与池塘水组肾小管中，特异性哇巴因结合也增加了一倍，分别为 20.7±2.3 与 9.1±0.9 飞摩尔/毫米肾小管长度，P<0.011。与池塘水组的肾小管（13.2±1.8 毫伏）相比，蒸馏水组肾小管中稀释段的跨上皮电位差增加（19.5±1.4 毫伏），P<0.015。我们得出结论，蒸馏水适应与特定的稀释段结构和功能改变有关，这可能与钠转运速率的增加有关。
