title: Rise of intracellular free calcium levels with activation of inositol triphosphate in a human colonic carcinoma cell line (COLO 205) by heat-stable enterotoxin of Escherichia coli.
abstract: The heat-stable enterotoxin (STa) produced by Escherichia coli has been found to increase rapidly two potential intracellular signals, inositol triphosphate and cytosolic free calcium in a human colonic cell line, COLO 205. Addition of STa to COLO 205 cells prelabelled with myo-[2-3H]inositol resulted in a rapid rise of [3H]inositol triphosphate. Using fluorescent indicator, Fura-2AM, intracellular free Ca2+ has been found to increase 5.12-fold compared to control. Suspension of cells in calcium-free buffer demonstrated STa-induced rapid rise of cytosolic Ca2+. The same result was found when extracellular calcium was chelated with EGTA. This effect was not observed with cells that were pretreated with dantrolene which suggest that the intracellular calcium rise might be due to mobilization from intracellular stores. This study demonstrated for the first time a change in cytosolic calcium in cultured human colonic cells by STa, which is accompanied by inositol triphosphate activation.
authors.affiliation: Division of Pathophysiology, National Institute of Cholera and Enteric Diseases, P-33, C.I.T. Road, Scheme-XM, Beliaghata, Calcutta 700 010, India.
authors.forename: J
authors.initials: J
authors.lastname: Bhattacharya
authors.forename: M K
authors.initials: MK
authors.lastname: Chakrabarti
mesh_terms: D001427:Bacterial Toxins / Q000008:administration & dosage / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D003110:Colonic Neoplasms / Q000378:metabolism; D003600:Cytosol / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004533:Egtazic Acid / Q000494:pharmacology; D004768:Enterotoxins / Q000008:administration & dosage / Q000494:pharmacology*; D029968:Escherichia coli Proteins; D005110:Extracellular Space / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism; D005456:Fluorescent Dyes; D016257:Fura-2 / Q000031:analogs & derivatives; D006801:Humans; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism*; D007295:Inositol Phosphates / Q000378:metabolism; D013997:Time Factors; D014316:Tritium; D014407:Tumor Cells, Cultured / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure
chemical_list: D001427:Bacterial Toxins; D004768:Enterotoxins; D029968:Escherichia coli Proteins; D005456:Fluorescent Dyes; D007295:Inositol Phosphates; C034151:heat stable toxin (E coli); D014316:Tritium; C049925:fura-2-am; D004533:Egtazic Acid; D015544:Inositol 1,4,5-Trisphosphate; D002118:Calcium; D016257:Fura-2