Uptake and Utilisation of Amino Acids by Human Hair Follicles and Related Cells

Riches, Caroline (1996). Uptake and Utilisation of Amino Acids by Human Hair Follicles and Related Cells. MPhil thesis The Open University.

DOI: https://doi.org/10.21954/ou.ro.0000ff44

Abstract

The requirements of amino acids as components of hair proteins, and the utilisation of glutamine by hair follicles to provide energy, point to the importance of amino acids in hair follicle metabolism. This thesis describes an investigation of the role of amino acids in hair follicles, with particular regard to cysteine and arginine. The cellular transport of amino acids into the outer root sheath (ORS) is examined, since this regulates their intracellular availability, and may thus affect hair formation.

The major findings of this study are as follows:

Both arginine and cysteine are essential for hair growth and protein synthesis. Cysteine plays a role in determining hair fibre diameter, as fibre thinning and growth retardation occur reversibly with diminishing cysteine supply. Hair follicles express the amino acid transporter ASC, which will provide an active mechanism for the uptake of cysteine. Serine uptake by ORS cells is inhibited by excess cysteine, and is sodium-dependent, consistent with transport by system ASC.

Arginine can be oxidised to carbon dioxide by hair follicles, and its availability affects lactate production by follicles, reflecting changes in energy metabolism. However, most of the arginine taken up by follicles is incorporated into protein, primarily (60%) in the hair root sheaths, and partly (30%) in the hair fibre. Hair follicles express the gene for system y⁺. Uptake of arginine by ORS cells is inhibited by excess lysine or ornithine, which is consistent with transport by system y⁺, although the electrogenic regulation normally associated with y⁺ was not clearly demonstrated.

The peptide transporters, PepTl and HPT-1, and the putative transport subunit/activator encoded by rBAT, do not appear to be expressed by hair follicles. It is also possible that there is no active glutamate transporter present, since glutamate is transported into ORS cells by a markedly slower mechanism than arginine, cysteine or serine.