Hormonal regulation of dipeptide transporter (PepT1) in Caco-2 cells with normal and anoxia/reoxygenation management.
OBJECTIVE
To determine the regulation effects of recombinant human growth hormone (rhGH) on dipeptide transporter(PepT1) in Caco-2 cells with normal culture and anoxia/reoxygenation injury.


METHODS
A human intestinal cell monolayer (Caco-2) was used as the in vitro model of human small intestine and cephalexin as the model substrate for dipeptide transporter (PepT1). Caco-2 cells grown on Transwell membrane filters were preincubated in the presence of rhGH in the culture medium for 4 d, serum was withdrawn from monolayers for 24 h before each experiment. The transport experiments of cephalexin across apical membromes were then conducted; Caco-2 cells grown on multiple well dishes (24 pore) with normal culture or anoxia/reoxygenation injury were preincubated with rhGH as above and uptake of cephalexin was then measured.


RESULTS
The transport and uptake of cephelaxin across apical membranes of Caco-2 cells after preincubation with rhGH were significantly increased compared with controls (P=0.045, 0.0223). Also, addition of rhGH at physiological concentration (34 nM) to incubation medium greatly stimulates cephalexin uptake by anoxia/reoxygenation injuried Caco-2 cells (P=0.0116), while the biological functions of PepT1 in injured Caco-2 cells without rhGH were markedly downregulated. Northern blot analysis showed that the level of PepT1 mRNA of rhGH-treated injured Caco-2 cells was greatly increased compared to controls.


CONCLUSIONS
The present results of rhGH stimulating the uptake and transport of cephalexin indicated that rhGH greatly upregulates the physiological effects of dipeptide transporters of Caco-2 cells. The alteration in the gene expression may be a mechanism of regulation of PepT1. In addition, Caco-2 cells take up cephalexin by the Proton-dependent dipeptide transporters that closely resembles the transporters present in the intestine. Caco-2 cells represent an ideal cellular model for future studies of the dipeptide transporter.
Sun
Bing-Wei
BW
Research Institute of General Surgery, Chinese PLA General Hospital of Nanjing Military Area, 305 East Zhongshan Road, Nanjing 210002, Jiangsu Province, China. sunbinwe@hotmail.com
Zhao
Xiao-Chen
XC
Wang
Guang-Ji
GJ
Li
Ning
N
Li
Jie-Shou
JS
D001483:Base Sequence; D001692:Biological Transport / Q000187:drug effects; D002352:Carrier Proteins / Q000187:drug effects / Q000378:metabolism*; D015687:Cell Hypoxia / Q000187:drug effects; D002506:Cephalexin / Q000493:pharmacokinetics; D003110:Colonic Neoplasms; D015342:DNA Probes; D004151:Dipeptides / Q000378:metabolism*; D019382:Human Growth Hormone / Q000494:pharmacology*; D006801:Humans; D007413:Intestinal Mucosa / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D007700:Kinetics; D008855:Microscopy, Electron, Scanning; D000074011:Peptide Transporter 1; D011994:Recombinant Proteins / Q000494:pharmacology; D027981:Symporters; D019108:Tight Junctions / Q000187:drug effects / Q000648:ultrastructure; D014407:Tumor Cells, Cultured
D002352:Carrier Proteins; D015342:DNA Probes; D004151:Dipeptides; D000074011:Peptide Transporter 1; D011994:Recombinant Proteins; C082186:SLC15A1 protein, human; D027981:Symporters; D019382:Human Growth Hormone; D002506:Cephalexin