Shpun S, Katz U
Department of Biology, Technion, Israel Institute of Technology, Haifa, Israel.
Physiol Biochem Zool. 1999 Mar-Apr;72(2):227-37. doi: 10.1086/316650.
Green toads (Bufo viridis) were acclimated to either tap water, 230 mOsmol NaCl kg-1 H2O (saline), 500 mOsmol NaCl kg-1 H2O (high saline), or 500 mmol L-1 urea. Renal functions for each acclimation group were studied on conscious animals that had one ureter chronically catheterized. Reciprocal immersion of tap-water- and saline-acclimated toads in the opposite solution did not stress the animals osmotically, and plasma osmolality increased or decreased by no more than 15%. However, urine osmolality and ionic composition changed immediately and profoundly on exposure to the other solution. Exposure of tap-water-acclimated toads to saline decreased urine flow by 30%, whereas the reciprocal immersion led to an increase of 30%. Immersion of tap-water-acclimated toads in high saline led to immediate cessation of urine flow, whereas immersion of 500 NaCl- or urea-acclimated toads in tap water led to a large increase in urine flow, with an overshoot that lasted 10 h (as a result of either salt or urea diuresis). Urine flow then stabilized at a level 5-6 times higher than the value attained at high-salt environment. On immersion of 500 urea-acclimated toads in 500 NaCl, urine flow doubled, accompanied by a change in ion composition, without change in the osmolality. In all experimental conditions, plasma potassium concentration was maintained within a narrow range. The results show that the toad's kidneys contributed efficiently both to osmo- and ionoregulation in a wide range of ambient solutions.
将绿蟾蜍（Bufo viridis）分别置于自来水、230 mOsmol NaCl kg⁻¹ H₂O（盐水）、500 mOsmol NaCl kg⁻¹ H₂O（高盐水）或500 mmol L⁻¹尿素中进行驯化。对一侧输尿管长期插管的清醒动物研究了每个驯化组的肾功能。将适应自来水和盐水的蟾蜍相互浸入相反的溶液中，不会对动物造成渗透压应激，血浆渗透压的升高或降低不超过15%。然而，尿液渗透压和离子组成在接触另一种溶液后立即发生了深刻变化。将适应自来水的蟾蜍暴露于盐水中，尿液流量减少30%，而反向浸入则导致尿液流量增加30%。将适应自来水的蟾蜍浸入高盐水中会导致尿液立即停止流动，而将适应500 NaCl或尿素的蟾蜍浸入自来水中会导致尿液流量大幅增加，并出现持续10小时的过冲现象（由于盐利尿或尿素利尿）。然后尿液流量稳定在比高盐环境下达到的值高5至6倍的水平。将适应500尿素的蟾蜍浸入500 NaCl中，尿液流量加倍，同时离子组成发生变化，而渗透压不变。在所有实验条件下，血浆钾浓度都维持在狭窄范围内。结果表明，蟾蜍的肾脏在广泛的环境溶液中对渗透压和离子调节都有高效作用。
