Shi M M, Stewart D J, Sen A K
Can J Biochem. 1980 Oct;58(10):1223-9. doi: 10.1139/o80-163.
Na+,K+-ATPase activity was monitored by measuring ouabain-sensitive K+-dependent p-nitrophenylphosphatase (p-NPPase) activity in rat submandibular gland slices. Carbachol (carbamylcholine chloride) stimulated the p-NPPase activity in the presence of calcium but not in its absence. Carbachol activation of the enzyme was totally ouabain sensitive and could be blocked by atropine. A minimal requirement of sodium ion extracellularly was required for this carbachol stimulation. cGMP and its dibutyryl analogue was also effective in stimulating the enzyme activity, whereas, cAMP was ineffective. Calcium, however, was not required for cGMP activation of the p-NPPase activity. The result indicates that calcium is the second messenger and cGMP is the tertiary connection between cholinergic stimulation and Na+,K+-ATPase activation in these glands. Activation of Na+,K+-ATPase is postulated to be responsible for primary fluid formation.
通过测量大鼠下颌下腺切片中哇巴因敏感的钾依赖性对硝基苯磷酸酶（p-NPPase）活性来监测Na⁺,K⁺-ATP酶活性。在有钙存在的情况下，卡巴胆碱（氯化氨甲酰胆碱）能刺激p-NPPase活性，但在无钙时则不能。该酶的卡巴胆碱激活作用完全对哇巴因敏感，且可被阿托品阻断。这种卡巴胆碱刺激需要细胞外钠离子的最低需求量。环鸟苷酸（cGMP）及其二丁酰类似物也能有效刺激该酶活性，而环腺苷酸（cAMP）则无效。然而，cGMP激活p-NPPase活性并不需要钙。结果表明，钙是第二信使，而cGMP是这些腺体中胆碱能刺激与Na⁺,K⁺-ATP酶激活之间的第三级联系。推测Na⁺,K⁺-ATP酶的激活负责初级液体的形成。
