Verdugo P
Center for Bioengineering, University of Washington, Seattle 98195.
Am Rev Respir Dis. 1991 Sep;144(3 Pt 2):S33-7. doi: 10.1164/ajrccm/144.3_pt_2.S33.
Mucins produced by goblet cells of the respiratory mucosa are condensed while stored in secretory granules. Mucin condensation and its decondensation upon exocytosis can be explained by the theory of polymer gel phase transition. After the opening of a secretory pore, Ca2+ inside the granule is exchanged for extracellular Na+. Na/Ca exchange triggers a polymer gel phase transition whereby the mucin polymer matrix undergoes massive swelling and thereby changes from a condensed to a hydrated phase. Swelling of the granular content is driven by a Donnan potential and results in the release of secretory product and the formation of small mucin gels, which later anneal to each other to form the respiratory mucus. Because of the tangled rather than cross-linked topology of the mucin network, the rheologic properties of the respiratory mucus depend primarily on hydration. As mucins are polyionic, the hydration of mucus is controlled by a Donnan equilibrium. Hence, mucus hydration and rheology are determined by two factors: the quantity, chain length, and charge density of the secreted mucins, and the amount and the ionic and polyionic composition of the water transported across the respiratory mucosa.
呼吸道黏膜杯状细胞产生的黏蛋白在储存于分泌颗粒时会发生浓缩。黏蛋白的浓缩及其在胞吐作用时的解浓缩可以用聚合物凝胶相变理论来解释。分泌孔打开后，颗粒内的Ca2+与细胞外的Na+进行交换。Na/Ca交换引发聚合物凝胶相变，由此黏蛋白聚合物基质发生大量膨胀，从而从浓缩相转变为水合相。颗粒内容物的膨胀由唐南电位驱动，导致分泌产物释放并形成小的黏蛋白凝胶，这些小凝胶随后相互融合形成呼吸道黏液。由于黏蛋白网络的拓扑结构是缠结而非交联的，呼吸道黏液的流变学特性主要取决于水合作用。由于黏蛋白是聚离子性的，黏液的水合作用由唐南平衡控制。因此，黏液的水合作用和流变学由两个因素决定：分泌的黏蛋白的数量、链长和电荷密度，以及跨呼吸道黏膜运输的水的量和离子及聚离子组成。
