Nishimura H, Imai M, Ogawa M
Am J Physiol. 1983 Mar;244(3):F247-54. doi: 10.1152/ajprenal.1983.244.3.F247.
Isolated segments of the renal tubules from the freshwater trout, Salmo gairdneri, were perfused in vitro to characterize ion and water transport. The distal tubule showed a transepithelial voltage (Vt) positive in the lumen (+17.8 +/- 1.4 mV). Furosemide added to the lumen and Na cyanide and ouabain added to the bath reduced the lumen-positive Vt of the distal tubule. Removal of either Cl- or Na+ from both perfusate and bathing medium abolished the lumen-positive Vt. When the distal tubule was perfused and bathed with isosmotic solution, net water flux (Jv) was nearly zero. Jv and hydraulic conductivity remained low when the osmolality of the bathing fluid was increased with raffinose. Neurohypophysial hormones added to the bath showed no effect. Chloride efflux (lumen to bath, 171.1 +/- 17.1 peq x mm-1. min-1) was significantly higher than chloride influx (bath to lumen, 105.6 +/- 12.3 peq x mm-1 x min-1), suggesting that net chloride reabsorption exists. These results suggest that in the freshwater trout, which lack the loop of Henle, the distal tubule acts as a diluting segment. The presence of sodium, in addition to chloride, is required to generate the lumen-positive Vt in the distal tubule.
对虹鳟（Salmo gairdneri）的离体肾小管节段进行体外灌注，以表征离子和水的转运。远端小管显示管腔内跨上皮电压（Vt）为正（+17.8±1.4 mV）。向管腔内添加呋塞米以及向浴液中添加氰化钠和哇巴因可降低远端小管管腔内为正的Vt。从灌注液和浴液中去除Cl-或Na+会消除管腔内为正的Vt。当用等渗溶液灌注和浸泡远端小管时，净水流（Jv）几乎为零。当用棉子糖提高浴液的渗透压时，Jv和水力传导率仍然很低。向浴液中添加神经垂体激素没有效果。氯外流（从管腔到浴液，171.1±17.1 peq x mm-1·min-1）显著高于氯内流（从浴液到管腔，105.6±12.3 peq x mm-1 x min-1），这表明存在氯的净重吸收。这些结果表明，在没有亨氏袢的虹鳟中，远端小管起到稀释段的作用。除了氯之外，还需要有钠才能在远端小管中产生管腔内为正的Vt。
