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一般认为胃粘膜的第一道防护机构是覆盖粘膜的被覆粘液层(粘液屏障)。该层是上皮厚度的几倍,是由富有糖链特性的粘液醣蛋白和白蛋白等血清蛋白所组成的高分子凝胶层,由高分子相互结合形成海绵状的多重网眼构造,具有粘性。第二道防护机构是粘膜上皮层(粘膜屏障)。根据Davenport的定义,“所谓粘膜屏障,就是阻止H~+向粘膜内的逆透过,防止Na~+从粘膜侧向胃内腔透过的性质”,但没有形态学的特异性。胃液中存在着由胃粘膜上皮分泌的HCO_3~-,这种HCO_5一遇到H~+就结合,形成H_2O和CO_2。由于迅速消失,难以检出。作者通过动物实验证实分泌到胃内腔的HCO_5~-依存在于血中HCO_3~-浓度的梯度,胃内浓度约占血中浓度的50%,在人体也证实了这种碱性分泌物。有人认为向胃内腔逸出的HCO_3~-虽然量很少(最大胃酸浓度的10%以下),但是对在粘液层保持逆扩散的H~+起一定程度的防御作用。给动物点滴盐酸使血中HCO_3~-下降,于胃内高酸的条件下发生溃疡性病变,这时如果使用碳酸脱氨酶抑制剂则溃疡变大加深。
The first protective mechanism of the gastric mucosa is generally considered to cover the mucosal covered mucus layer (mucus barrier). This layer is several times the thickness of the epithelium. It is a macromolecule gel layer composed of mucosal glycoproteins rich in sugar chains and serum proteins such as albumin, which are aggregated with polymers to form a sponge-like multiple network structure and have adhesiveness. The second protective agency is the mucosal epithelium (mucosal barrier). According to Davenport’s definition, “the so-called mucosal barrier is the property of preventing the reverse transmigration of H ~ + into the mucosa and preventing the permeation of Na ~ + from mucosal side to the gastric cavity”, but there is no morphological specificity. Gastric juice exists in gastric epithelial secretion of HCO_3 ~ -, this HCO_5 on the encounter H ~ +, the formation of H_2O and CO_2. Due to its rapid disappearance, it is difficult to detect it. The animal experiments confirmed that the secretion of HCO_5 ~ - secreted into the gastric cavity is dependent on the gradient of HCO_3 ~ in the blood, and the concentration in the stomach is about 50% of the blood concentration. This alkaline secretion is also confirmed in the human body. It is thought that HCO 3 - released to the gastric cavity is small in quantity (less than 10% of maximum gastric acid concentration), but has a certain degree of defensive action against H ~ + that maintains a counter diffusion in the mucus layer. Hydrochloric acid is added to the animal to lower HCO 3 - in the blood, and ulcerative lesions occur in the high acid in the stomach. At this time, the ulcer is deepened and deepened if the carbon dioxide deaminase inhibitor is used.