Chabardès D, Montégut M, Imbert-Teboul M, Morel F
Mol Cell Endocrinol. 1984 Oct;37(3):263-75. doi: 10.1016/0303-7207(84)90096-0.
A microradioimmunoassay for cAMP was developed in order to analyse the effects of alpha-adrenergic agonists on vasopressin (AVP)-induced cAMP cell accumulation in single pieces of microdissected medullary (MCT) and cortical (CCT) rat collecting tubules. Under the experimental conditions chosen (4 min of incubation in the presence of a phosphodiesterase inhibitor), no cAMP could be detected either in the bathing solution or in non-stimulating samples of tubule. In MCT, 10(-6) M AVP stimulated cAMP generation up to 128.3 +/- 9.0 (SEM) fmoles per mm of tubule per 4 min, N = 11. The response was dose-dependent with a KA value below 10(-10) M AVP. The addition of norepinephrine (NE) (10(-5) M in the presence of propranolol) suppressed the larger part of the response to AVP (from 92% with 2 X 10(-11) M AVP to 76% with 10(-6) M AVP); the addition of 10(-7) M NE still reduced by 59% the MCT response to 10(-10) M AVP (26.2 +/- 5.9 vs. 64.0 +/- 6.4 fmoles/mm, N = 3). In CCT, 10(-5) M NE reduced by 84% the cAMP generation induced by 10(-10) M AVP (8.8 +/- 2.0 vs. 54.2 +/- 3.5 fmoles/mm, N = 3). This inhibitory action of NE against the AVP effect in CCT was mimicked by 10(-7) M clonidine; in MCT it was suppressed by phentolamine and yohimbine, but not by prazosin, suggesting that alpha 2-adrenoreceptors are involved. On the other hand, the addition of the alpha-agonists to the incubation solution produced no inhibition of the cAMP cell accumulations induced by glucagon, calcitonin and isoproterenol in CCT, or glucagon in MCT, an observation demonstrating that alpha 2-adrenergic agonists selectively inhibit vasopressin-dependent cAMP generation by these nephron segments.
为了分析α-肾上腺素能激动剂对微解剖的大鼠髓质集合管（MCT）和皮质集合管（CCT）中血管加压素（AVP）诱导的cAMP细胞积累的影响，开发了一种用于cAMP的微量放射免疫测定法。在所选的实验条件下（在磷酸二酯酶抑制剂存在下孵育4分钟），在浴液或肾小管的非刺激样品中均未检测到cAMP。在MCT中，10^(-6) M AVP刺激cAMP生成，每4分钟每毫米肾小管可达128.3±9.0（SEM）飞摩尔，N = 11。该反应呈剂量依赖性，AVP的KA值低于10^(-10) M。加入去甲肾上腺素（NE）（在普萘洛尔存在下为10^(-5) M）可抑制对AVP反应的大部分（从2×10^(-11) M AVP时的92%降至10^(-6) M AVP时的76%）；加入10^(-7) M NE仍使MCT对10^(-10) M AVP的反应降低59%（26.2±5.9对64.0±6.4飞摩尔/毫米，N = 3）。在CCT中，10^(-5) M NE使10^(-10) M AVP诱导的cAMP生成降低84%（8.8±2.0对54.2±3.5飞摩尔/毫米，N = 3）。NE对CCT中AVP作用的这种抑制作用被10^(-7) M可乐定模拟；在MCT中，它被酚妥拉明和育亨宾抑制，但不被哌唑嗪抑制，这表明涉及α2-肾上腺素能受体。另一方面，在孵育溶液中加入α-激动剂对CCT中胰高血糖素、降钙素和异丙肾上腺素诱导的cAMP细胞积累或MCT中胰高血糖素诱导的cAMP细胞积累没有抑制作用，这一观察结果表明α2-肾上腺素能激动剂选择性抑制这些肾单位节段中血管加压素依赖性cAMP的生成。
