Safranow Krzysztof, Korzonek Maria, Dziedziejko Violetta, Jakubowska Katarzyna, Sulzyc-Bielicka Violetta, Domański Leszek, Ciechanowski Kazimierz, Chlubek Dariusz
Pomorska Akademia Medyczna w Szczecinie, Katedra i Zakład Biochemii i Chemii.
Pol Merkur Lekarski. 2006 Feb;20(116):168-72.
Vitamin C is present as ascorbic acid (Asc) with antioxidative properties and as its oxidation product dehydroascorbic acid (dAsc). Asc is actively transported from blood to gastric juice where it prevents formation of carcinogenic nitrosamines and protects mucosa from reactive oxygen species. Another important function of gastric mucosa is proton pump-dependent secretion of hydrochloric acid. The pump maintains high pH gradient between gastric juice and plasma. The aim of the work was to analyse relations between gastric juice pH and concentrations of Asc and dAsc in plasma, gastric mucosa and juice as well as other factors modifying metabolism of vitamin C and function of gastric mucosa.
31 patients were subjected to diagnostic endoscopy due to dyspepsia. Concentrations of Asc and dAsc were measured in plasma, gastric mucosa and juice with HPLC method. pH of gastric juice was determined. Histopathology examination of mucosa and urease test for Helicobacter pylori were performed. Data concerning dyspeptic symptoms and used drugs, including vitamin C preparations, were collected.
Patients taking vitamin C preparations had significantly lower gastric juice pH values than the others (median 2.2 vs 5.4; p < 0.01). Treatment with vitamin C preparations was also associated with higher Asc concentrations in gastric juice (median 16.6 vs. 1.8 micromol/L; p < 0.09); the difference was statistically significant in the subgroup of patients with gastritis (median 16.6 vs. 0.1 micromol/L; p < 0.04). Strong negative correlations of pH with Asc (Rs = -0.67; p < 0.001) and dAsc (Rs = -0.48; p < 0.01) concentrations were observed in gastric juice. Positive correlation of pH and relative dAsc content expressed as percent of total vitamin C concentration in gastric juice was also statistically significant (Rs = +0.48; p < 0.05).
Performance of the proton pump and vitamin C metabolism in the stomach are closely mutually connected. Modification of hydrochloric acid secretion may affect gastric juice vitamin C concentration. Potentially disadvantageous influence of antisecretory drugs on the mechanisms of antioxidative protection in the stomach needs further investigation.
维生素C以具有抗氧化特性的抗坏血酸（Asc）及其氧化产物脱氢抗坏血酸（dAsc）的形式存在。Asc从血液被主动转运至胃液，在胃液中它可防止致癌性亚硝胺的形成，并保护黏膜免受活性氧的损伤。胃黏膜的另一重要功能是质子泵依赖的盐酸分泌。该泵维持着胃液与血浆之间的高pH梯度。本研究的目的是分析胃液pH与血浆、胃黏膜及胃液中Asc和dAsc浓度之间的关系，以及其他影响维生素C代谢和胃黏膜功能的因素。
31例因消化不良接受诊断性内镜检查的患者。采用高效液相色谱法测定血浆、胃黏膜及胃液中Asc和dAsc的浓度。测定胃液的pH。对黏膜进行组织病理学检查，并进行幽门螺杆菌尿素酶试验。收集有关消化不良症状及所用药物（包括维生素C制剂）的数据。
服用维生素C制剂的患者胃液pH值显著低于未服用者（中位数2.2对5.4；p<0.01）。服用维生素C制剂还与胃液中较高的Asc浓度相关（中位数16.6对1.8μmol/L；p<0.09）；在胃炎患者亚组中差异具有统计学意义（中位数16.6对0.1μmol/L；p<0.04）。在胃液中观察到pH与Asc（Rs=-0.67；p<0.001）及dAsc（Rs=-0.48；p<0.01）浓度呈强负相关。胃液pH与以胃液中总维生素C浓度百分比表示的相对dAsc含量之间的正相关也具有统计学意义（Rs=+0.48；p<0.05）。
胃中质子泵的功能与维生素C代谢密切相关。盐酸分泌的改变可能影响胃液中维生素C的浓度。抗分泌药物对胃中抗氧化保护机制的潜在不利影响需要进一步研究。
