Fedirko N V, Kruglikov I A, Kopach O V, Vats J A, Kostyuk P G, Voitenko N V
Biological Department, I.Franko Lviv National University, 4 Grushevsky St., Lviv 79005, Ukraine.
Biochim Biophys Acta. 2006 Mar;1762(3):294-303. doi: 10.1016/j.bbadis.2005.12.002. Epub 2005 Dec 29.
Xerostomia and pathological thirst are troublesome complications of diabetes mellitus associated with impaired functioning of salivary glands; however, their cellular mechanisms are not yet determined. Isolated acinar cells were loaded with Ca2+ indicators fura-2/AM for measuring cytosolic Ca2+ concentration ([Ca2+]i) or mag-fura-2/AM-inside the endoplasmic reticulum (ER). We found a dramatic decrease in pilocarpine-stimulated saliva flow, protein content and amylase activity in rats after 6 weeks of diabetes vs. healthy animals. This was accompanied with rise in resting [Ca2+]i and increased potency of acetylcholine (ACh) and carbachol (CCh) but not norepinephrine (NE) to induce [Ca2+]i transients in acinar cells from diabetic animals. However, [Ca2+]i transients mediated by Ca2+ release from ER stores (induced by application of either ACh, CCh, NE, or ionomycin in Ca2+-free extracellular medium) were decreased under diabetes. Application of inositol-1,4,5-trisphosphate led to smaller Ca2+ release from ER under the diabetes. Both plasmalemma and ER Ca2+-ATPases activity was reduced and the latter showed the increased affinity to ATP under the diabetes. We conclude that the diabetes caused impairment of salivary cells functions that, on the cellular level, associates with Ca2+ overload, increased Ca2+-mobilizing ability of muscarinic but not adrenergic receptors, decreased Ca2+-ATPases activity and ER Ca2+ content.
口干症和病理性口渴是糖尿病的麻烦并发症，与唾液腺功能受损有关；然而，它们的细胞机制尚未确定。分离的腺泡细胞用Ca2+指示剂fura-2/AM加载，用于测量胞质Ca2+浓度（[Ca2+]i），或用mag-fura-2/AM加载到内质网（ER）内。我们发现，与健康动物相比，糖尿病大鼠在6周后毛果芸香碱刺激的唾液流量、蛋白质含量和淀粉酶活性显著降低。这伴随着静息[Ca2+]i的升高以及乙酰胆碱（ACh）和卡巴胆碱（CCh）而非去甲肾上腺素（NE）诱导糖尿病动物腺泡细胞[Ca2+]i瞬变的能力增强。然而，在糖尿病状态下，由内质网储存释放Ca2+介导的[Ca2+]i瞬变（通过在无Ca2+细胞外培养基中应用ACh、CCh、NE或离子霉素诱导）减少。在糖尿病状态下，应用肌醇-1,4,5-三磷酸导致内质网释放的Ca2+减少。糖尿病状态下，质膜和内质网Ca2+-ATP酶活性均降低，且后者对ATP的亲和力增加。我们得出结论，糖尿病导致唾液细胞功能受损，在细胞水平上，这与Ca2+过载、毒蕈碱受体而非肾上腺素能受体的Ca2+动员能力增加、Ca2+-ATP酶活性降低和内质网Ca2+含量降低有关。
