Role of nitric oxide in NAG-ST induced store-operated calcium entry in rat intestinal epithelial cells.
This study was undertaken to find out the mechanism of non-agglutinable Vibrio cholerae heat-stable enterotoxin (NAG-ST)-induced calcium influx across the plasma membrane. Adriamycin, an inhibitor of IP3-specific 3-kinase, could not inhibit NAG-ST-induced calcium influx in rat intestinal epithelial cells, which suggested that inositol 1,3,4,5-tetrakisphosphate (IP4) had no role in NAG-ST-induced calcium influx. NAG-ST increased intracellular nitric oxide level of rat enterocytes as measured by a fluorimetric method using a fluoroprobe 4,5-diaminofluorescein-2-diacetate (DAF-2DA). N-Nitro-L-arginine, an inhibitor of nitric oxide synthase, inhibited NAG-ST-induced rise in nitric oxide level and also calcium influx. Inhibition of inositol trisphosphate (IP3)-mediated intracellular calcium mobilization by Dantrolene could also inhibit NAG-ST-induced rise in intracellular nitric oxide level. Moreover, inhibition of soluble guanylate cyclase by inhibitors (ODQ, LY83583) could inhibit the NAG-ST-induced rise in cyclic guanosine-3',5'-monophosphate (cGMP) level and calcium influx. From this study, it is evident that NAG-ST causes IP3-mediated calcium release from intracellular calcium store, which then stimulates nitric oxide production by activating nitric oxide synthase and the nitric oxide through cGMP activates calcium influx.
Pathophysiology Division, National Institute of Cholera and Enteric Diseases, P-33, C.I.T. Road, Scheme-XM, Beliaghata, Calcutta 700010, India.
Kazi Mirazul
KM
Hoque
Subhrajit
S
Saha
Dyuti Datta
DD
Gupta
Manoj K
MK
Chakrabarti
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D004768:Enterotoxins / Q000633:toxicity*; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D007413:Intestinal Mucosa / Q000187:drug effects* / Q000378:metabolism; D009569:Nitric Oxide / Q000502:physiology*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors*; D051381:Rats
D004768:Enterotoxins; D004791:Enzyme Inhibitors; C037420:stN protein, Vibrio cholerae; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D002118:Calcium