Molecular mechanisms underlying age-dependent decrease of water transport in salivary glands and the investigation of the drug in xerostomia

乙酰胆碱对衰老大鼠腮腺腺细胞顶质膜（APM）水通道蛋白-5丰度的刺激作用明显低于青壮年大鼠。在本研究中，我们寻找在衰老大鼠腮腺APM中AQP5持续增加的药物。顺式-2-甲基螺-（1,3-氧硫代烷-5,3′）-喹诺定诱导腮腺组织APM中AQP5呈剂量依赖性增加，EC_<50>值为14.2±2.3 nM。顺式-2-甲基螺-（1,3-氧硫代烷-5,3′）-喹啉-和匹罗卡平诱导的APM中AQP5的增加分别在10 min和3 min时达到最大，并持续时间超过30 min。pF-HHSiD、U73122、丹曲林或TMB-8均能抑制这种增加，但GF 109203X无抑制作用。在细胞外CaCl_2存在的情况下，顺式-2-甲基螺-（1,3-草酸硫烷-5,3′）-喹啉在分离的腺泡细胞中诱导了[Ca^<2+>]i的显著和持续振荡。这些结果表明，顺式-2-甲基螺-（1,3-草酸硫烷-5,3′）-喹啉作用于M_3受体，诱导腮腺腺腺APM中AQP5的量持续增加，这种作用是通过肌醇1,4,5-三磷酸和ryanodine受体从细胞内储存中释放Ca^<2+>介导的。顺式-2-甲基螺-(1,3-草酸硫烷-5,3')-奎诺列定诱导顶质膜中水通道蛋白-5的量持续增加，这与年轻成年大鼠和衰老大鼠腮腺组织相似，表明该药物对治疗年龄相关性口干症有效。

The stimulatory effect of acetylcholine, but not that of epinephrine, on the abundance of aquaporin-5 in the apical plasma membrane (APM) of parotid acinar cells was markedly reduced in tissue from senescent rats relative to that in tissue from young adult animals. In this study, we looked for the drug which persistent increase in the amount AQP5 in the APM of-parotid glands of senescent rats.cis-2-methylspiro-(1,3-oxathiolane-5,3')-quinuclidine induced a marked increase of AQP5 in the APM of parotid tissues in a dose-dependent manner with an EC_<50> value of 14.2 ± 2.3 nM. cis-2-methylspiro-(1,3-oxathiolane-5,3')-quinuclidine- and pilocarpine-induced increase in the amount of AQP5 in the APM was maximal at 10 and 3 min, respectively, and persisted for longer than 30 min. This increase was inhibited by pF-HHSiD, U73122, dantrolene or TMB-8, but not by GF 109203X. In the presence of extracellular CaCl_2, cis-2-methylspiro- (1,3- oxathiolane-5,3')-quinuclidine induced marked and persistent oscillations in [ Ca^<2+> ]i in isolated acinar cells. These results suggest that cis-2-methylspiro-(1,3- oxathiolane-5,3')-quinuclidine acts at M_3 receptors to induce a persistent increase in the amount of AQP5 in APM of parotid acini, and that this effect is mediated by the release of Ca^<2+> from intracellular stores through both inositol 1,4,5-trisphosphate and ryanodine receptors.The cis-2-methylspiro-(1,3-oxathiolane-5,3')-quinuclidine induced a persistent increase in the amount of aquaporin-5 in the apical plasma membrane that was similar for parotid tissue from young adult and senescent rats, suggesting that this drug prove effective for treatment of age-related xerostomia.