Walcott Benjamin, Birzgalis Aija, Moore Leon C, Brink Peter R
Centre for Visual Sciences, Research School of Biological Sciences, Australian National University, PO Box 475, Canberra ACT 2601, Australia.
Am J Physiol Cell Physiol. 2005 Oct;289(4):C860-7. doi: 10.1152/ajpcell.00526.2004. Epub 2005 May 25.
We have previously suggested that fluid flow in the mouse exorbital lacrimal gland is driven by the opening of apical Cl- and K+ channels. These ions move into the lumen of the gland and water follows by osmosis. In many tissues, the Na+-K+-2Cl- cotransporter (NKCC1) replaces the Cl- and K+ ions that move into the lumen. We hypothesize that mouse exorbital lacrimal glands would have NKCC1 co-transporters and that they would be important in fluid transport by this gland. We used immunocytochemistry to localize NKCC1-like immunoreactivity to the membranes of the acinar cells as well as to the basolateral membranes of the duct cells. We developed a method to measure tear flow and its composition from mouse glands in situ. Stimulation with the acetylcholine agonist carbachol produced a peak flow followed by a plateau. Ion concentration measurements of this stimulated fluid showed it was high in K+ and Cl-. Treatment of the gland with furosemide, a blocker of the NKCC1 cotransporter, reduced the plateau phase of fluid flow by approximately 30%. Isolated cells exposed to a hypertonic shock shrank by approximately 20% and then showed a regulatory volume increase (RVI). Both the RVI and swelling were blocked by treatment with furosemide. Cells isolated from these glands shrink by approximately 10% in the presence of carbachol. Blocking NKCC1 with furosemide reduced the amount of shrinkage by approximately 50%. These data suggest that NKCC1 plays an important role in fluid secretion by the exorbital gland of mice.
我们之前曾提出，小鼠眶外泪腺中的液体流动是由顶端氯离子和钾离子通道的开放所驱动的。这些离子进入腺腔，水通过渗透作用随之进入。在许多组织中，钠-钾-2氯协同转运蛋白（NKCC1）会补充进入腺腔的氯离子和钾离子。我们推测小鼠眶外泪腺会有NKCC1协同转运蛋白，并且它们在该腺体的液体运输中很重要。我们使用免疫细胞化学方法将NKCC1样免疫反应定位到腺泡细胞的膜以及导管细胞的基底外侧膜上。我们开发了一种方法来原位测量小鼠腺体的泪液流量及其成分。用乙酰胆碱激动剂卡巴胆碱刺激会产生一个流量峰值，随后是一个平台期。对这种刺激产生的液体进行离子浓度测量显示，其钾离子和氯离子含量很高。用呋塞米（一种NKCC1协同转运蛋白的阻滞剂）处理腺体，可使液体流动的平台期减少约30%。暴露于高渗休克的分离细胞会收缩约20%，然后出现调节性容积增加（RVI）。RVI和肿胀都被呋塞米处理所阻断。从这些腺体分离出的细胞在卡巴胆碱存在的情况下会收缩约10%。用呋塞米阻断NKCC1可使收缩量减少约50%。这些数据表明NKCC1在小鼠眶外腺体的液体分泌中起重要作用。
