Roediger W E, Radcliffe B C
Cell Physiology Laboratory, University of Adelaide, Queen Elizabeth Hospital, Woodville, Australia.
Gastroenterology. 1988 Apr;94(4):915-22. doi: 10.1016/0016-5085(88)90547-1.
Colonic levels of nitrite and circulating levels of nitrate are elevated in subjects with chronic diarrhea. The role of colonic epithelial cells in oxidation-reduction of nitrite and consequent control of nitrite and nitrate levels is unknown. Isolated rat colonocytes and isolated loops of colon were used to study oxidation and reduction of nitrate and nitrite. Colonocytes oxidized nitrite to nitrate at a rate of 162 +/- 33 nmol/min.g (dry wt) (n = 6) over 0-20 min, a value increased by addition of 5 mM glucose and 1 mM nicotinamide adenine dinucleotide (p = less than 0.01), but not altered by antibiotics. Nitrite oxidation correlated linearly with the dry weight of isolated colonocytes (r = 0.92), indicating a cellular reaction. Nitrite was absorbed at a rate of 0.28 nmol/min.cm2 (n = 9) from the colonic lumen, which reflected 74% absorption of the available nitrite. Of the absorbed nitrite, 14.3% reappeared in the colonic lumen as nitrate. Colonocytes may be important in oxidizing nitrite to nitrate, thus preventing excess nitrite from entering into the circulation and returning some nitrate to the colonic lumen for respiration by anaerobic bacteria. The interaction of nitrites and colonocytes deserves further study with regard to the oxidation-reduction of nitrite and to the development of colonic neoplasia in chronic diarrheal conditions.
慢性腹泻患者结肠中的亚硝酸盐水平和循环中的硝酸盐水平会升高。结肠上皮细胞在亚硝酸盐的氧化还原以及由此对亚硝酸盐和硝酸盐水平的控制中所起的作用尚不清楚。本研究利用分离的大鼠结肠细胞和结肠肠袢来研究硝酸盐和亚硝酸盐的氧化与还原。结肠细胞在0至20分钟内将亚硝酸盐氧化为硝酸盐的速率为162±33 nmol/分钟·克（干重）（n = 6），添加5 mM葡萄糖和1 mM烟酰胺腺嘌呤二核苷酸后该值增加（p < 0.01），但不受抗生素影响。亚硝酸盐氧化与分离的结肠细胞干重呈线性相关（r = 0.92），表明这是一种细胞反应。亚硝酸盐从结肠腔以0.28 nmol/分钟·平方厘米的速率被吸收（n = 9），这反映了74%的可用亚硝酸盐被吸收。在吸收的亚硝酸盐中，14.3%以硝酸盐的形式重新出现在结肠腔中。结肠细胞在将亚硝酸盐氧化为硝酸盐方面可能很重要，从而防止过量亚硝酸盐进入循环，并将一些硝酸盐返回结肠腔以供厌氧菌呼吸。关于亚硝酸盐的氧化还原以及慢性腹泻情况下结肠肿瘤的发生，亚硝酸盐与结肠细胞之间的相互作用值得进一步研究。
