What is the mechanism of ascorbic acid absorption?
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Ascorbic acid absorption involves multiple mechanisms. One mechanism is a saturable, stereospecific, Na+-dependent transporter that allows ascorbic acid to accumulate in osteoblast cells at a high concentration . Another mechanism involves the glucose transporter GLUT1, which transports dehydroascorbic acid (DHA) into cells and then traps it as ascorbic acid . Ascorbate can be reversibly oxidized to dehydroascorbic acid, which can cross cell membranes . The presence of separate transport mechanisms with different kinetics, tissue specificity, and Na+ and energy dependence supports this . In the aqueous humor, ascorbic acid transport from the ciliary body to the aqueous humor involves a co-transport system for 2 Na+ and 1 ascorbate, as well as a Na+-independent transport mechanism for DHA . The existence of a non-passive, saturable process for ascorbic acid absorption in humans has been confirmed .
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64 Citations | The paper suggests the existence of a non-passive, saturable process for ascorbic acid absorption in humans. However, the specific mechanism of ascorbic acid absorption is not mentioned in the paper. |
Open access•Journal Article 01 Jan 1990-Fortschritte der Ophthalmologie : Zeitschrift der Deutschen Ophthalmologischen Gesellschaft 4 Citations | The paper discusses two mechanisms for the absorption of ascorbic acid: (1) co-transport with 2 Na+ ions and 1 ascorbate, and (2) Na(+)-independent transport of the oxidized form of ascorbic acid (dehydro-ascorbic acid) in cooperation with intracellular DHA reductase. |
182 Citations | The paper does not provide a clear answer to the mechanism of ascorbic acid absorption. |
10 Citations | The mechanism of ascorbic acid absorption is different in osteoblast cells and leukocytes. Osteoblast cells use a saturable, stereospecific, Na+-dependent transporter, while leukocytes use the glucose transporter GLUT1 to absorb dehydroascorbic acid (DHA). |
Related Questions
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What is the mechanism of the UV-vis absorbance of ascorbic acid?3 answersThe mechanism of the UV-vis absorbance of ascorbic acid involves several factors. Firstly, it has been observed that the absorption of UV radiation by ascorbic acid can lead to the formation of free radicals, which can then undergo further reactions. Additionally, the presence of ascorbic acid has been found to quench the fluorescence of tryptophan and protein in the eye media, thereby minimizing UV radiation to the lens. Furthermore, the presence of ascorbic acid has been shown to hinder the photodegradation of collagen molecules under UV radiation, potentially through the formation of hydrogen bonds between ascorbic acid and collagen. Finally, the absorbance of ascorbic acid itself can be affected by the presence of other substances, such as the Fe3+-Clofibric Acid complex, which has been shown to mediate the oxidation of ascorbic acid.
What is the dosage of ascorbic acid?5 answersThe dosage of ascorbic acid varies depending on the specific study and its purpose. In one study, type 2 diabetic patients were supplemented with either 250 mg/day or 1,000 mg/day of ascorbic acid. Another study investigated the electrochemical oxidation of ascorbic acid in various aqueous solutions, but did not specify a dosage. A different study mentioned that doses of up to 5 g of ascorbic acid daily can be administered safely, and even higher doses may be used in therapeutic trials. In a study on chromium poisoning, L-ascorbic acid therapy was used at a concentration of 30 μg/mL. Finally, a study on ascorbic acid absorption found that the maximum amount of ascorbic acid that can be absorbed in 24 hours is 1160 mg. Overall, the dosage of ascorbic acid can vary depending on the specific context and purpose of the study.
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