Characterization of zinc (Zn) transport across Caco-2 cell monolayers

Description/Abstract

Colonic carcinoma Caco-2 cells grown as a monolayer exhibit many of the characteristics of the small intestine including inducibility of metallothionein by Zn. The authors have now characterized the transport of Zn across confluent, 14 day in vitro Caco-2 monolayers grown on polycarbonate support membranes. Both uptake and transport across the cells were linear for at least 10 min. Zn cell uptake in the mucosa-to-serosa (m-s) direction was saturable, with a K{sub t} = 23.8 {plus minus} 7.8 {mu}M. J{sub max} was 0.46 {plus minus} 0.08 {mu}mol/cm{sup 2} {times} 10 min. Transcellular passage was concentration dependent. In the (s-m) direction, the K{sub t} of Zn cell uptake was 59 {plus minus} 13 {mu}M and that of the transcellular transport was 103 {plus minus} 53 {mu}M. Cell uptake J{sub max} was 0.98 {plus minus} 0.11 {mu}mol/cm{sup 2} {times} 10 min, and transcellular transport J{sub max} was 2.90 {plus minus} 0.47 {mu}mol/cm{sup 2} {times} 10 min. Low molecular weight ligands (histidine, cysteine, proline or glutathione at 1 mM each), added to the mucosal side, did not alter Zn cell uptake or transmembrane passage. Potential transport inhibitors such as ouabain or vanadate, or metabolic inhibitors also had no effect. Zn transport and cell uptake by Caco-2 cells are kinetically comparable to those of in vivo systems and could serve as a valid model for Zn absorption studies.