This chapter contains sections titled: Nutritional aspects of dietary proteins Digestion of proteins Absorption of protein digestion products Fate of absorbed protein digestion products Physiological and clinical significance Regulation of amino acid and peptide absorption Protein-energy malnutrition Defects in digestion and absorption of proteins References

OBJECTIVE:ATB(0,+) is an energy-coupled transporter for arginine and amino acid-based prodrugs. The objective of the study was to examine the expression of this transporter in cervical cancer. METHODS:Specimens of normal ectocervical mucosa and cervical squamous cell carcinoma were used for determination of ATB(0,+) mRNA levels by RT-PCR. A commercial dot blot of paired normal cervix and cervical cancer cDNA was also used to quantify ATB(0,+) mRNA. ATB(0,+) mRNA and protein in tissue sections were analyzed by in situ hybridization and immunohistochemistry/immunofluorescence. RESULTS:ATB(0,+) mRNA increased 5.6-fold (P < 0.0004) in cervical cancer compared to normal cervix. This was associated with a parallel increase in ATB(0,+) protein. CONCLUSIONS:Expression of ATB(0,+) is minimal in normal cervix and is up-regulated in cervical cancer. The up-regulation of this highly concentrative transporter for arginine and prodrugs in cervical cancer has significant clinical and therapeutic relevance.

Purpose. The purpose of this study was to analyze the transport of amino acid esters and the amino-acid-based prodrug valganciclovir by the Na+/Cl−-coupled amino acid transporter ATB0,+.