Volume-activated taurine transport is differentially activated in human cervical cancer HT-3 cells but not in human papillomavirus-immortalized Z183A and normal cervical epithelial cells.
1. Previous studies demonstrate that volume-sensitive chloride currents are distinctly activated in cervical cancer cells, but not in human papillomavirus (HPV)-immortalized and normal cervical cells. In the present study, the Na(+)-independent volume-activated transport of taurine in three cervical cell types was investigated. 2. Osmotic swelling of cervical cancer HT-3 cells suspended in Na(+)-free hypotonic medium led to increased membrane uptake of taurine. This taurine uptake was effectively blocked by various Cl- channel blockers with a similar potency in blocking volume-sensitive Cl- channels: 1,9-dideoxyforskolin > 5-nitro-2-(3-phenyl-propylamino)-benzoic acid (NPPB) > 4-acetamido-4'-isothiocyanastilbene-2,2'-disulphonic acid (SITS) > 4,4'-diisothio-cyanatostilbene-2,2-disulphonic acid (DIDS) > furosemide. The taurine influx was also abolished by pertussis toxin. In contrast, Na(+)-independent volume-activated taurine transport was not significantly activated in HPV-immortalized Z183A cells and in normal cervical cells. 3. Exposure of HT-3 cells to hypotonic medium also resulted in a marked increase in taurine efflux. The volume-activated taurine efflux was osmolarity dependent and the pattern of pharmacological inhibition by Cl- channel blockers was indistinguishable from that for taurine uptake. 4. These results suggest that volume-sensitive Cl- channels in HT-3 cells can mediate the transport of amino acids. In addition, the pertussis toxin-sensitive G-protein is linked with the activation of this transport mechanism.
Chou
C Y
CY
Department of Obstetrics and Gynecology, National Cheng Kung University Medical College, Tainan, Taiwan. chougyn@mail.ncku.edu.tw
Shen
M R
MR
Chen
T M
TM
Huang
K E
KE
D001693:Biological Transport, Active / Q000187:drug effects; D048429:Cell Size / Q000502:physiology; D002472:Cell Transformation, Viral; D002584:Cervix Uteri / Q000166:cytology / Q000378:metabolism* / Q000821:virology*; D018118:Chloride Channels / Q000037:antagonists & inhibitors / Q000378:metabolism; D004847:Epithelial Cells / Q000378:metabolism; D005260:Female; D006801:Humans; D007038:Hypotonic Solutions; D009997:Osmotic Pressure; D027383:Papillomaviridae; D013654:Taurine / Q000493:pharmacokinetics*; D014316:Tritium; D014407:Tumor Cells, Cultured; D002583:Uterine Cervical Neoplasms / Q000378:metabolism* / Q000473:pathology
D018118:Chloride Channels; D007038:Hypotonic Solutions; D014316:Tritium; D013654:Taurine