A sodium-dependent transport system is responsible for transfer and distribution of vitamins to different parts of the body, the transfer includes vitamins like pantothenate, biotin, and ascorbic acid etc, These transporters belong to Solute Carrier family (SLC). Since vitamins are required for essential metabolic processes in all mammalian cells, such cells have developed intrinsic mechanisms to active accumulation of essential vitamins. Thus transporters help these cells to fulfill their requirement, they include Sodium-dependent Multi-Vitamin Transporter (SMVT), Sodium-dependent Vitamin-C Transporter (SVCT) 1 & 2, Creatine Transporter (CRT1/ CT1). The other vitamin transporters from SLC family include Thiamine Transporter Protein 1 (THTR1), Folate Transporter or Reduced Folate Carrier 1 (RFC1), Thyroid Iodide Transporter (TIT) and Taurine Transporter (TAU) etc.

Sodium-dependent Multi-Vitamin Transporter (SMVT), a 635aa protein in rat and human (gene SLC5A6) is responsible for transplacental transfer of vitamins pantothenate, biotin and the essential metabolite lipoate. SMVT shows homology to other known sodium-dependent nutrient transporters, including bacterial pantothenate permease, mammalian iodide transporter, glucose transporter 1 & 2. Quantitatively, the absorptive tissues like the intestinal mucosa, kidney and placenta have very high amounts of SMVT-specific mRNA. Significant amount is also seen in liver, brain, and heart.

Sodium-dependent Vitamin C Transporter (SVCT), Vitamin C is now known to mediate a variety of enzymatic reactions, including collagen synthesis, the basis for the defect in scurvy, the vitamin also protects tissues from oxidative damage by scavenging free radical. The vitamin C absorption and distribution requires SVCT1 and SVCT2.

SVCT1 605aa protein in rat, 604 in human (chrm 5, gene SLC23A1) contain up to 12 transmembrane domains, two possible sites for N-glycosylation and multiple phosphorylation sites. It is 65% identical to SVCT2 and largely expressed in epithelial surfaces involved in bulk transport such as intestine, liver and kidney.

SVCT2 account for tissue specific uptake of Vit C, expression is widespread occurring in neurons, bone and other tissues. SVCT2 is a 592aa protein in rat and 650aa long in human (chrm 20, gene SLC23A2). It is predominantly prenatal Vit C transporter to most tissues particularly in central nervous system and adrenal glands. Deficiency to this protein is lethal in newborn mice.

Creatine Transporter/ CRT1 or CT1 (mouse, human 635 aa, chromosome X28) is expressed in kidney, muscle, brain, and other tissues. A specific uptake system for creatine has been demonstrated in skeletal muscle, human monocytes, macrophages, and astroglial-rich cultures. Since muscle cells do not synthesize creatine, the creatine-phosphocreatine shuttle has important functions in the temporal and spatial maintenance of the energy supply to skeletal and cardiac muscle.

Thiamine Transporter Protein 1 (THTR1), a 498aa protein in mouse and 497 in human (chrm 1q23.3, gene SLC19A2) is a high affinity transporter for the intake of Thiamine, Most abundantly found in skeletal and cardiac muscle, lower levels are seen in placenta, heart, liver and kidney. Defects in gene are the cause of Thiamine Responsive Megaloblastic Anemia (TRMA)

Folate Transporter/ FOLT/ RFC, a 512aa each protein in mouse and rat, 591aa in human (chrm 21q22.3, gene SLC19A1) transports folate compounds into mammalian cells via receptor mediated or carrier mediated mechanisms, as such maintains the intracellular concentration of folate. It shows 65% identity to mouse and hamster folate transporters

Thyroid Iodide Transporter (TIT), a 618aa protein in rat with 12 transmembrane domains, with both N and C termini to be cytoplasmic. It transports Iodide at cellular level mediated by intrinsic membrane Na+/ I+ symporter, since iodide is an essential constituent of thyroid hormones.

Taurine Transporter (TAU), Taurine is a major intracellular amino acid in mammals involved in a number of important physiological processes. The Taurine transport is cells depend on Na+ & Cl- ions and is localized in basolateral plasma membrane. A 621aa protein in rat and 619aa in human (chrm 3p25.q24, gene SLC6A6) TAU regulates hypertonicity by intracellular accumulation of high concentrations of small organic solutes. Widely expressed in ileal, mucosa, brain, and liver.