INTESTINAL-ABSORPTION OF WATER-SOLUBLE VITAMINS IN CHANNEL CATFISH (ICTALURUS-PUNCTATUS)
INTESTINAL-ABSORPTION OF WATER-SOLUBLE VITAMINS IN CHANNEL CATFISH (ICTALURUS-PUNCTATUS)
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DOI：
10.1152/ajpregu.1995.269.3.r490
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发表时间：
1995-09-01
影响因子：
2.8
通讯作者：
FERRARIS, RP
中科院分区：
文献类型：
--
作者：
CASIROLA, DM;VINNAKOTA, RR;FERRARIS, RP
研究了斑点叉尾（Ictalurus punctatus）离体肠袖对水溶性维生素的吸收。核黄素和生物素的摄取均被其未标记形式抑制，表明存在饱和机制[核黄素：米氏常数（Km），4.84 +/- 1.23 μ M;最大速度（V-max），0.59 +/- 0.07 pmol。mg（-1）。min（-1）生物素：K-m，22.3 +/- 6.95 μ M; V-max 0.67 +/- 0.10 pmol。mg（-1）。min（-1）]。相反，烟酰胺、叶酸及其代谢衍生物5-甲基四氢叶酸的摄取并没有被它们各自的非标记形式显著抑制。它们的摄取是浓度的线性函数[解离常数，0.173 +/- 0.006，0.050 +/- 0.002和0.031 +/- 0.004 pmol。mg（-1）。min（-1）μ M（-1）]。叶酸比5-甲基四氢叶酸吸收更快，两种维生素都不抑制另一种的吸收。核黄素和生物素的肠道摄取是载体介导的，而烟酰胺、叶酸和5-甲基四氢叶酸的摄取是通过简单扩散发生的。这些机制类似于在哺乳动物中发现的相同维生素，除了疏水性叶酸，其在哺乳动物中被积极运输，但扩散可能足以满足鲶鱼的代谢需求。
The absorption of selected water-soluble vitamins was studied in isolated intestinal sleeves of channel catfish (Ictalurus punctatus). The uptakes of riboflavin and biotin were each inhibited by their nonlabeled form, indicating the presence of a saturable mechanism [riboflavin: Michaelis constant (K-m), 4.84 +/- 1.23 mu M; maximal velocity (V-max), 0.59 +/- 0.07 pmol . mg(-1). min(-1) biotin: K-m, 22.3 +/- 6.95 mu M; V-max 0.67 +/- 0.10 pmol . mg(-1). min(-1)]. In contrast, uptakes of nicotinamide, folic acid, and its metabolic derivative 5-methyltetrahydrofolate were not significantly inhibited by their respective nonlabeled forms. Their uptakes were a linear function of concentration [dissociation constant, 0.173 +/- 0.006, 0.050 +/- 0.002, and 0.031 +/- 0.004 pmol . mg(-1). min(-1).mu M(-1), respectively]. Folic acid was absorbed more rapidly than 5-methyltetrahydrofolate, and neither vitamin inhibited the absorption of the other. Intestinal uptake of riboflavin and biotin is carrier mediated, whereas uptake of nicotinamide, folic acid, and 5-methyltetrahydrofolate occurs by simple diffusion. These mechanisms are similar to those found in mammals for the same vitamins, except for the hydrophobic folates, which are actively transported in mammals but where diffusion may suffice to fulfill metabolic requirements of catfish.