Baum M, Quigley R
Departments of Pediatrics and Internal Medicine, The University of Texas Southwestern Medical Center at Dallas, Dallas, Texas, USA.
Kidney Int. 1998 Nov;54(5):1593-600. doi: 10.1046/j.1523-1755.1998.00156.x.
Dopamine can produce a natriuresis and diuresis independent of changes in renal hemodynamics. However, previous studies have failed to demonstrate an inhibition of transport by dopamine in intact proximal convoluted tubules.
Rabbit proximal convoluted tubules were perfused in vitro with an ultrafiltrate-like solution and bathed in a serum-like albumin solution.
In the present study, the addition of 10-5 M dopamine to the lumen or bath of proximal convoluted tubules perfused in vitro had no effect on transport. In proximal convoluted tubules, addition of 10-6 M bath norepinephrine increased the rate of volume absorption from 0.65 +/- 0.08 to 0.93 +/- 0.08 nl/mm. min (P < 0.01). Addition of 10-5 M luminal dopamine in the presence of bath norepinephrine inhibited the rate of volume absorption to 0.72 +/- 0.10 nl/mm. min (P = 0.01). The inhibition in the rate of volume absorption by luminal dopamine in the presence of bath norepinephrine was completely blocked by the DA1 antagonist, SCH 23390. The DA1 agonist luminal 10-5 M fenoldopam also inhibited volume absorption in the presence of bath norepinephrine, but the DA2 agonist luminal 10-5 M quinpirole was without effect. Bath 10-5 M dopamine had no effect on volume absorption in the presence of bath norepinephrine.
Dopamine has no direct epithelial action on the proximal convoluted tubule. However, luminal dopamine antagonizes the stimulation in transport produced by norepinephrine. These studies suggest that luminal dopamine may play a role to modulate sodium transport in the presence of renal nerve activity.
多巴胺可产生利钠和利尿作用，且独立于肾血流动力学变化。然而，既往研究未能证实多巴胺对完整近端曲管转运的抑制作用。
采用类似超滤液的溶液对兔近端曲管进行体外灌注，并置于类似血清白蛋白溶液中。
在本研究中，向体外灌注的近端曲管管腔或浴液中添加10⁻⁵M多巴胺对转运无影响。在近端曲管中，添加10⁻⁶M浴液去甲肾上腺素可使容积吸收率从0.65±0.08增加至0.93±0.08 nl/mm·min（P<0.01）。在浴液中有去甲肾上腺素存在时添加10⁻⁵M管腔多巴胺可使容积吸收率抑制至0.72±0.10 nl/mm·min（P = 0.01）。在浴液中有去甲肾上腺素存在时，管腔多巴胺对容积吸收率的抑制作用被DA1拮抗剂SCH 23390完全阻断。管腔10⁻⁵M非诺多泮这种DA1激动剂在浴液中有去甲肾上腺素存在时也可抑制容积吸收，但管腔10⁻⁵M喹吡罗这种DA2激动剂则无作用。浴液中10⁻⁵M多巴胺在浴液中有去甲肾上腺素存在时对容积吸收无影响。
多巴胺对近端曲管无直接上皮作用。然而，管腔多巴胺可拮抗去甲肾上腺素对转运的刺激作用。这些研究提示，在肾神经活动存在时，管腔多巴胺可能在调节钠转运中发挥作用。
