Hayslett J P, Macala L J, Smallwood J I, Kalghatgi L, Gasalla-Herraiz J, Isales C
Department of Internal Medicine, Yale School of Medicine, New Haven, Connecticut, USA.
Kidney Int. 1995 Jun;47(6):1576-84. doi: 10.1038/ki.1995.221.
Studies were performed to determine the primary signal transduction mechanism that mediates adenosine stimulation of electrogenic sodium transport in renal epithelial cells. Experiments were performed on cultured amphibian A6 cells with an adenosine analogue that preferentially binds to the A1 receptor, cyclohexyladenosine (CHA). Sodium transport was assessed by the equivalent short circuit current (Ieq). CHA was found to stimulate Ieq via activation of an A1 receptor because (1) the threshold concentration was 1 nM compared to that of 10 microM for the specific A2 agonist CGS21680, (2) CHA inhibited vasopressin (AVP)-stimulated cAMP production by a pertussis toxin-sensitive mechanism, and (3) the action of CHA was inhibited by the A1 antagonist 1,3-dipropyl-8-cyclopentylxanthine (DPCPX). CHA increased intracellular Ca2+ ([Ca2+]i) and stimulated phosphoinositide turnover at concentrations that increased Ieq and in a time course that paralleled the increase in Ieq. Ion transport was stimulated by a Ca(2+)-dependent mechanism because the CHA induced increase in Ieq was inhibited by chelating [Ca2+]i with 5,5'dimethyl BAPTA in a dose-dependent manner, with a Ki of approximately 10 microM. The increase in Ieq was also dose-dependently inhibited by the specific PKC inhibitors dihydroxychlorpromazine and chelerythrine, and by trifluoperazine which inhibits PKC and calmodulin. Further studies indicated that CHA-stimulated Ieq was independent of cAMP generation because CHA did not induce an increase in cAMP accumulation parallel to the increase in Ieq in a dose-response analysis, and the adenylate cyclase inhibitor 2',5' dideoxy-adenosine (DDA) did not affect the CHA-induced increase in Ieq.(ABSTRACT TRUNCATED AT 250 WORDS)
开展了多项研究以确定介导腺苷刺激肾上皮细胞中电生性钠转运的主要信号转导机制。使用优先与A1受体结合的腺苷类似物环己基腺苷（CHA），对培养的两栖类A6细胞进行实验。通过等效短路电流（Ieq）评估钠转运。发现CHA通过激活A1受体刺激Ieq，原因如下：（1）与特异性A2激动剂CGS21680的10 microM阈值浓度相比，CHA的阈值浓度为1 nM；（2）CHA通过百日咳毒素敏感机制抑制血管加压素（AVP）刺激的cAMP产生；（3）CHA的作用被A1拮抗剂1,3 - 二丙基 - 8 - 环戊基黄嘌呤（DPCPX）抑制。CHA在增加Ieq的浓度下并在与Ieq增加平行的时间进程中增加细胞内Ca2+（[Ca2+]i）并刺激磷脂酰肌醇周转。离子转运由Ca（2+）依赖性机制刺激，因为用5,5' - 二甲基BAPTA螯合[Ca2+]i以剂量依赖性方式抑制CHA诱导的Ieq增加，Ki约为10 microM。Ieq的增加也被特异性PKC抑制剂二羟基氯丙嗪和白屈菜红碱以及抑制PKC和钙调蛋白的三氟拉嗪剂量依赖性抑制。进一步研究表明，CHA刺激的Ieq与cAMP生成无关，因为在剂量反应分析中，CHA不会诱导与Ieq增加平行的cAMP积累增加，并且腺苷酸环化酶抑制剂2'，5' - 二脱氧腺苷（DDA）不影响CHA诱导的Ieq增加。（摘要截断于250字）
