Baumann K, Bode F, Papavassiliou F
Curr Probl Clin Biochem. 1976;6:123-33.
In order to reveal the sidedness of the cyclic AMP action on renal tubules the effect of cyclic nucleotides on isotonic fluid reabsorption was examined in proximal convoluted rat kidney tubules by using advanced micropuncture techniques. Cyclic AMP inhibited isotonic fluid reabsorption preferentially when applied on the luminal cell side. This finding coincides with a predominant distribution of a membrane bound cyclic AMP dependent protein kinase in a luminal cell membrane fraction. On the luminal cell side cyclic AMP and dibutyryl cyclic AMP inhibited isotonic fluid reabsorption in a similar dose dependent behaviour. Concentrations of both nucleotides as low as 10-10M had a definite inhibitory effect. Tested at a high concentration N6-butyryl cyclic AMP was almost as effective as cyclic AMP. Deoxy cyclic AMP, 5' AMP, cyclic GMP and dibutyryl cyclic GMP had no effect. ATP inhibited isotonic fluid reabsorption to a very small extent. The data indicate that the observed inhibition of isotonic fluid reabsorption is specific for cyclic AMP and that the interaction of cyclic AMP and the luminal cell membrane is initiated at the luminal cell surface.
为了揭示环磷酸腺苷（cAMP）对肾小管作用的单侧性，采用先进的微穿刺技术，研究了环核苷酸对大鼠近曲肾小管等渗液重吸收的影响。当将cAMP应用于管腔侧细胞膜时，它优先抑制等渗液的重吸收。这一发现与膜结合的环磷酸腺苷依赖性蛋白激酶在管腔侧细胞膜部分的主要分布相一致。在管腔侧细胞膜，cAMP和二丁酰环磷酸腺苷（dbcAMP）以相似的剂量依赖性方式抑制等渗液重吸收。两种核苷酸低至10^-10M的浓度都有明确的抑制作用。在高浓度下测试时，N6-丁酰环磷酸腺苷几乎与cAMP一样有效。脱氧环磷酸腺苷、5'-腺苷酸（5'AMP）、环磷酸鸟苷（cGMP）和二丁酰环磷酸鸟苷（dbcGMP）均无作用。三磷酸腺苷（ATP）在很小程度上抑制等渗液重吸收。数据表明，观察到的等渗液重吸收抑制对cAMP具有特异性，并且cAMP与管腔侧细胞膜的相互作用始于管腔侧细胞表面。
