Wei J W, Yeh S R, Wang E K
Institute of Neurosciences, National Yang-Ming Medical College, Taipei, Taiwan, Republic of China.
Chin J Physiol. 1991;34(3):303-15.
The biochemical events which are coupled to the subtypes of muscarinic cholinergic receptors in rat salivary glands were studied. The subtype property of this receptor system was characterized by the use of 3H-QNB binding to glandular membrane homogenates. The Kd and Bmax values of this binding were found to be 0.2 nM and 210 fmole/mg protein respectively. In the drug-displacement study on the 3H-QNB binding the following potency order was obtained (based on the IC50 values calculated from each individual dose-response curve): Atropine greater than 4-DAMP greater than HHSiD greater than Pirenzepine greater than AF-DX 116. This order is a typical M3 muscarinic subtype, according to the recent consensus. Carbachol (0.1 mM) caused a 4.4-fold increased in IP3 production over the basal level, when tissue fragments were prelabeled with 3H-inositol. The above mentioned cholinergic antagonists could block this event in a similar potency order. Carbachol (0.1 mM) did not have a significant effect on the basal level of cAMP formation of these tissue homogenates. On the other hand, it had a 33% reduction of isoproterenol (10 microM)-enhancing cAMP formation. The reduction effect of carbachol on cAMP formation could also be blocked by the above mentioned cholinergic antagonists in a similar order. Our results indicated that rat salivary glands have M3 muscarinic receptors and the activation of these receptors causes changes in both phosphatidylinositol turnover and cAMP formation.
本研究探讨了大鼠唾液腺中与毒蕈碱型胆碱能受体亚型相关的生化事件。该受体系统的亚型特性通过用3H-QNB结合腺膜匀浆来表征。此结合的Kd和Bmax值分别为0.2 nM和210 fmol/mg蛋白质。在3H-QNB结合的药物置换研究中，得到以下效价顺序（基于从各剂量-反应曲线计算的IC50值）：阿托品＞4-DAMP＞HHSiD＞哌仑西平＞AF-DX 116。根据最近的共识，该顺序是典型的M3毒蕈碱亚型。当组织切片用3H-肌醇预标记时，卡巴胆碱（0.1 mM）使IP3生成量比基础水平增加了4.4倍。上述胆碱能拮抗剂能以相似的效价顺序阻断这一事件。卡巴胆碱（0.1 mM）对这些组织匀浆的cAMP基础生成水平无显著影响。另一方面，它使异丙肾上腺素（10 μM）增强的cAMP生成减少了33%。卡巴胆碱对cAMP生成的减少作用也能被上述胆碱能拮抗剂以相似顺序阻断。我们的结果表明，大鼠唾液腺具有M3毒蕈碱受体，这些受体的激活会导致磷脂酰肌醇代谢和cAMP生成的变化。
