Nakahari T, Morimatsu S, Imai Y
Dept. Physiology, Osaka Medical College, Takatsuki, Japan.
Eur J Morphol. 1998 Aug;36 Suppl:107-11.
The effects of HCO3- on fluid secretory rate, cell volume and tissue structure were studied in perfused submandibular salivary glands under hyposmotic conditions (240 mosM). Fluid secretion was elicited by acetylcholine (ACh) in a hyposmotic HCO3(-)-free solution. Upon switching the perfusate from the HCO3(-)-free to the HCO3(-)-containing solution during ACh stimulation, the fluid secretory rate exhibited a small transient increase followed by a sharp decrease. ACh stimulation evoked rapid cell shrinkage in the absence of HCO3-, but upon switching from the HCO3(-)-free to the HCO3(-)-containing solution during ACh stimulation, the acinar cells exhibited increases in volume. In laser confocal microscopic examination of isolated acini, fluorescence of lucifer yellow was detected in the lateral intercellular spaces during ACh stimulation in the absence of HCO3-, but not in the presence of HCO3-. Electron microscopic examination revealed similar findings. We propose that the occlusion of the lateral intercellular space induced by cell swelling may result in an increase in the resistance to fluid flow in the space and consequently a decrease in the fluid secretion rate. Maintenance of an open lateral intercellular space may be an important requirement for fluid secretion. These observations suggest that a paracellular pathway may play a significant role in salivary fluid secretion.
在低渗条件（240 mosM）下，对灌注的下颌下唾液腺中HCO3-对液体分泌速率、细胞体积和组织结构的影响进行了研究。在无HCO3-的低渗溶液中，乙酰胆碱（ACh）可引发液体分泌。在ACh刺激期间，当灌注液从无HCO3-溶液切换为含HCO3-溶液时，液体分泌速率先出现短暂小幅增加，随后急剧下降。在无HCO3-的情况下，ACh刺激可引起细胞迅速收缩，但在ACh刺激期间从无HCO3-溶液切换为含HCO3-溶液时，腺泡细胞体积增大。在激光共聚焦显微镜检查分离的腺泡时，在无HCO3-的ACh刺激期间，在细胞间外侧间隙检测到荧光黄荧光，但在有HCO3-时未检测到。电子显微镜检查也得到了类似结果。我们认为，细胞肿胀引起的细胞间外侧间隙阻塞可能导致该间隙中液体流动阻力增加，从而导致液体分泌速率下降。维持开放的细胞间外侧间隙可能是液体分泌的重要条件。这些观察结果表明，细胞旁途径可能在唾液分泌中起重要作用。
