Mechanism of heat acclimation-induced improvement of salivary secretion in rats

本研究探讨了热应激改善大鼠唾液腺功能的机制。两天热暴露增加大鼠下颌下腺水通道蛋白（AQP）1和5 mRNA的表达，同时促进HIF-1a通路，导致VEGF诱导。热暴露2 ~ 5d后，AQP 1蛋白水平升高。热习服后，AQP 5在浆液性腺泡细胞的顶膜分布增强，而AQP 1仅表达于下颌下腺内皮细胞。自发运动40 d可使大鼠下颌下腺AQP 1蛋白水平升高，但对AQP 5表达及与AQP 5诱导有关的TRPV 1、V3和Na-K ATP酶蛋白水平无影响。毛果芸香碱诱导的唾液分泌略有升高。这些结果表明，在大鼠中，热暴露或运动促进唾液腺中AQP的表达，这可能有助于改善唾液腺功能。

We investigated mechanism of heat exposure-induced improvement of salivary function in rats. Two-day heat exposure increased expressions of aquaporin (AQP)1 and 5 mRNA in submandibular glands of rats concomitant with the promotion of the HIF-1a pathway, leading to VEGF induction. The protein level of AQP1 was raised after 2 or 5 day-heat exposure. The apical membrane distribution of AQP5 in serous acinar cells enhanced after heat acclimation, while AQP1 expression was restricted to the endothelial cells in the submandibular glands. Spontaneous exercise for 40 days tended to elevate AQP1 protein level of the rat submandibular glands, whereas it failed to affect AQP5 expression and protein levels of TRPV1, V3 or Na-K ATPase, relating to induce AQP5. Pilocarpine-induced salibary secretion was slightly elevated. These results suggest that in rats, heat exposure or exercise facilitates AQP expression in salivary glands, which may then contribute to improving saliva gland function.