title: [Cellular and intracellular transport of vitamin C. The physiologic aspects].
abstract: Vitamin C requirement is satisfied by natural sources and vitamin C supplements in the ordinary human diet. The two major forms of vitamin C in the diet are L-ascorbic acid and L-dehydroascorbic acid. Both ascorbate and dehydroascorbate are absorbed along the entire length of the human intestine. The reduced form, L-ascorbic acid is imported by an active mechanism, requiring two sodium-dependent vitamin C transporters (SVCT1 and SVCT2). The transport of the oxidized form, dehydroascorbate is mediated by glucose transporters GLUT1, GLUT3 and possibly GLUT4. Initial rate of uptake of both ascorbate and dehydroascorbate is saturable with increasing external substrate concentration. Vitamin C plasma concentrations are tightly controlled when the vitamin is taken orally. It has two simple reasons, on the one hand, the capacity of the transporters is limited, on the other hand the two Na+-dependent transporters can be down-regulated by an elevated level of ascorbate.
authors.affiliation: Semmelweis Egyetem, Általános Orvostudományi Kar Orvosi Vegytani Molekuláris Biológiai és Patobiokémiai Intézet Budapest Tűzoltó u. 34-47. 1097 Budapesti Műszaki és Gazdaságtudományi Egyetem Alkalmazott Biotechnológia és Élelmiszer-tudományi Tanszék, Biokémiai és Molekuláris Biológiai Laboratórium Budapest.
authors.forename: András
authors.initials: A
authors.lastname: Szarka
authors.forename: Tamás
authors.initials: T
authors.lastname: Lőrincz
mesh_terms: D000975:Antioxidants / Q000378:metabolism; D001205:Ascorbic Acid / Q000097:blood / Q000378:metabolism*; D001692:Biological Transport; D002462:Cell Membrane / Q000378:metabolism; D003683:Dehydroascorbic Acid / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism; D051272:Glucose Transporter Type 1 / Q000378:metabolism; D051274:Glucose Transporter Type 3 / Q000378:metabolism; D051275:Glucose Transporter Type 4 / Q000378:metabolism; D006801:Humans; D007408:Intestinal Absorption; D008928:Mitochondria / Q000378:metabolism; D060347:Sodium-Coupled Vitamin C Transporters / Q000378:metabolism; D014815:Vitamins / Q000378:metabolism
chemical_list: D000975:Antioxidants; D051272:Glucose Transporter Type 1; D051274:Glucose Transporter Type 3; D051275:Glucose Transporter Type 4; C555162:SLC23A1 protein, human; C555163:SLC23A2 protein, human; C495677:SLC2A1 protein, human; C495687:SLC2A3 protein, human; C495692:SLC2A4 protein, human; D060347:Sodium-Coupled Vitamin C Transporters; D014815:Vitamins; D001205:Ascorbic Acid; D003683:Dehydroascorbic Acid
keywords: C-vitamin; napi ajánlott bevitel; recommended daily allowance; transport; transzport; vitamin C