Transport characteristics of L-carnosine and the anticancer derivative 4-toluenesulfonylureido-carnosine in a human epithelial cell line

Purpose. The aim of the present study was to evaluate whether the transepithelial transport of the anticancer compound 4-toluenesulfonylureido-carnosine (Ts-carnosine) and the dipeptide moiety L-carnosine was due to a hPepT1 carrier-mediated flux. Methods. Transport experiments were conducted using Caco-2 cell monolayers and either reversed-phase HPLC-UV or liquid scintillation counting methods for quantification. pK(a), LogD, and LogP were determined using the Sirius GlpK(a) meter. Results. L-carnosine was transported across the apical membrane with a K-m,K-app of 2.48+/-1.16 mM and a V-max of 2.08+/-0.34 nmol.cm(-2).min(-1) and across the basolateral membrane with a K-m,K-app of 7.21+/-3.17 mM and a V-max of 0.54+/-0.10 nmol.cm(-2).min(-1), and transepithelially with a P-app of 4.46.10(-2)+/-6.4.10(-6) cm.min-(10). Ts-carnosine had an affinity (K-i) for hPepT1 of 2.33+/-0.54 mM; however, the transepithelial transport was low as compared to that of L-carnosine. Conclusions. L-carnosine was transported across both the apical and basolateral membrane of Caco-2 cell monolayers in a carrier-mediated manner however, the transepithelial transport followed apparent simple non-saturable kinetics. Ts-carnosine had an affinity for hPepT1 but a relatively low transepithelial transport. This indicates that the transepithelial transport of L-carnosine and Ts-carnosine is not hPepT1 carrier-mediated and that L-carnosine is not a suitable dipeptide moiety for hPepT1-mediated absorption of sulfonamide-type anticancer compounds.