Skorecki K L, Conte J M, Ausiello D A
Miner Electrolyte Metab. 1987;13(3):165-72.
The activation of adenylate cyclase by vasopressin in the renal medulla takes place in a hypertonic environment whose osmolality fluctuates widely under varying physiologic conditions. We utilized the cultured renal epithelial cell line, LLC-PK1 as a model system to study the effects of hypertonic electrolyte and nonelectrolyte solutes on the vasopressin-adenylate cyclase interaction. These cells do not produce prostaglandins, thus permitting separate evaluation of the direct effects of hypertonic solutes on the adenylate cyclase response. In intact cells, 40-400 mM NaCl and 600 mM sucrose and mannitol increased basal and vasopressin-sensitive cAMP production 2 to 4-fold. Urea in a concentration range of 300-1,200 mM blunted the stimulatory effect of hypertonic NaCl in intact cells. In order to distinguish direct effects of solutes on the adenylate cyclase response, from effects related to hypertonic cell shrinkage, the influence of these same electrolyte and nonelectrolyte solutes on adenylate cyclase activity in membrane particulate fractions was also examined. Increasing NaCl in the concentration range of 25-100 mM increased basal and vasopressin-sensitive adenylate cyclase. This effect was not specific to sodium, since similar degrees of stimulation were seen with the addition of KCl. Addition of higher concentrations of NaCl, sucrose, and mannitol directly in the adenylate cyclase assay were inhibitory. These findings suggested that the stimulatory effect of hypertonicity in the intact cells was not due to a direct effect of these solutes on the enzyme, but rather to hypertonic cell shrinkage.(ABSTRACT TRUNCATED AT 250 WORDS)
血管加压素在肾髓质中激活腺苷酸环化酶是在高渗环境中发生的，该环境的渗透压在不同生理条件下波动很大。我们利用培养的肾上皮细胞系LLC-PK1作为模型系统，研究高渗电解质和非电解质溶质对血管加压素-腺苷酸环化酶相互作用的影响。这些细胞不产生前列腺素，因此可以单独评估高渗溶质对腺苷酸环化酶反应的直接影响。在完整细胞中，40-400 mM的NaCl以及600 mM的蔗糖和甘露醇可使基础和血管加压素敏感的cAMP生成增加2至4倍。300-1200 mM浓度范围内的尿素减弱了完整细胞中高渗NaCl的刺激作用。为了区分溶质对腺苷酸环化酶反应的直接影响与高渗性细胞皱缩相关的影响，还研究了这些相同的电解质和非电解质溶质对膜微粒部分中腺苷酸环化酶活性的影响。在25-100 mM浓度范围内增加NaCl可提高基础和血管加压素敏感的腺苷酸环化酶活性。这种作用并非钠所特有，因为添加KCl时也观察到了相似程度的刺激。在腺苷酸环化酶测定中直接添加更高浓度的NaCl、蔗糖和甘露醇具有抑制作用。这些发现表明，完整细胞中高渗性的刺激作用并非由于这些溶质对该酶的直接作用，而是由于高渗性细胞皱缩。（摘要截短于250字）
