Nezu Akihiro, Morita Takao, Nagai Takeharu, Tanimura Akihiko
Department of Pharmacology, School of Dentistry, Health Sciences University of Hokkaido, Ishikari-Tobetsu, Hokkaido, 061-0293, Japan.
Department of Biochemistry, The Nippon Dental University School of Life Dentistry at Niigata, 1-8 Hamaura-cho, Chuo-ku, Niigata, 951-8580, Japan.
Exp Physiol. 2019 Jan;104(1):61-69. doi: 10.1113/EP086868. Epub 2018 Nov 23.
What is the central question of this study? The effects of Ca responses on salivary fluid secretion have been studied indirectly by monitoring ion channel activities and other indices. Therefore, Ca responses during salivary secretion remain poorly understood. What is the main finding and its importance? Herein, we developed a simultaneous monitoring system for Ca responses and salivary secretion in live animals using a YC-Nano50-expressing submandibular gland and a fibre-optic pressure sensor. This new approach revealed a clear time lag between the onset of Ca responses and salivary secretion. We also estimated the [Ca ] and provided direct evidence for the regulation of salivary secretion by small increases in [Ca ] in submandibular gland acinar cells.
We monitored changes in [Ca ] during salivary secretion in the rat submandibular gland in live animals using a combination of intravital Ca imaging with the ultrasensitive Ca indicator YC-Nano50 and a fibre-optic pressure sensor. Intravenous infusion of ACh (10-720 nmol min ) increased [Ca ] and salivary flow rate in a dose-dependent manner. Repetitive stimulation with ACh induced equivalent Ca responses and salivary secretion in the same individual animals. The accurate ACh stimulation experiments revealed a clear time lag between the onset of the increase in [Ca ] and salivary secretion. The time lag with the lowest dose of ACh (30 nmol min ) was 106 s, which shortened to 19 s with the dose used for maximal salivary secretion (360 nmol min ). This time lag might reflect the time required for [Ca ] to reach the level required to activate molecules for fluid secretion. The resting [Ca ] in submandibular gland was 37 nm, and [Ca ] at the onset of salivary secretion was 45-57 nm, irrespective of ACh dose. These results indicate that low [Ca ] is sufficient to trigger fluid secretion in the rat submandibular gland in vivo.
本研究的核心问题是什么？通过监测离子通道活性和其他指标间接研究了钙反应对唾液分泌的影响。因此，唾液分泌过程中的钙反应仍知之甚少。主要发现及其重要性是什么？在此，我们使用表达YC-Nano50的下颌下腺和光纤压力传感器，开发了一种用于实时监测活体动物钙反应和唾液分泌的同步监测系统。这种新方法揭示了钙反应开始与唾液分泌之间存在明显的时间滞后。我们还估算了[Ca]，并为下颌下腺腺泡细胞中[Ca]的小幅升高对唾液分泌的调节提供了直接证据。
我们结合使用超灵敏钙指示剂YC-Nano50进行活体钙成像和光纤压力传感器，监测了活体动物大鼠下颌下腺唾液分泌过程中[Ca]的变化。静脉注射乙酰胆碱（10 - 720 nmol/min）以剂量依赖方式增加了[Ca]和唾液流速。在同一只动物中，重复给予乙酰胆碱刺激可诱导等效的钙反应和唾液分泌。精确的乙酰胆碱刺激实验揭示了[Ca]升高开始与唾液分泌之间存在明显的时间滞后。最低剂量乙酰胆碱（30 nmol/min）时的时间滞后为106秒，而用于最大唾液分泌的剂量（360 nmol/min）时缩短至19秒。这种时间滞后可能反映了[Ca]达到激活液体分泌分子所需水平所需的时间。下颌下腺的静息[Ca]为37 nM，唾液分泌开始时的[Ca]为45 - 57 nM，与乙酰胆碱剂量无关。这些结果表明，低[Ca]足以在体内触发大鼠下颌下腺的液体分泌。
