Evidence of calcium influx across the plasma membrane depends upon the initial rise of cytosolic calcium with activation of IP(3) in rat enterocytes by heat-stable enterotoxin of Vibrio cholerae non-O1.
In response to heat-stable enterotoxin of Vibrio cholerae non-O1, the initial rise of cytosolic Ca(2+) occurred with activation of IP(3). Chelation of extracellular Ca(2+) with EGTA and suspension of cells in Ca(2+) free buffer both demonstrated the involvement of internal stores in the rise of [Ca(2+)]i. Cells pretreated with dantrolene resulted in decrease of [Ca(2+)]i response which suggested that the rise of intracellular level of Ca(2+) was mostly due to the mobilization from IP(3) sensitive stores. When the cytosolic Ca(2+) was chelated by loading the cells with BAPTA, NAG-ST could not induce Ca(2+) entry to the cell as assessed by Mn(2+) quenching of fura-2 fluorescence which suggested that calcium influx across the plasma membrane depends upon initial rise of this bivalent cation that maintained the sustained phase of [Ca(2+)]i response. Addition of toxin to the fura-2-loaded cells, preincubated with lanthanum chloride, resulted in reduction of [Ca(2+)]i level with a short duration of irregular sustained phase further suggesting that the influx of Ca(2+) across the plasma membrane might be through the calcium channel.
Pathophysiology Division, national Institute of Cholera and Enteric Diseases, Calcutta, India.
K M
KM
Hoque
A
A
Pal
G B
GB
Nair
S
S
Chattopadhyay
M K
MK
Chakrabarti
D000818:Animals; D002021:Buffers; D002118:Calcium / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D003620:Dantrolene / Q000494:pharmacology; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D020895:Enterocytes / Q000187:drug effects / Q000378:metabolism*; D004768:Enterotoxins / Q000633:toxicity*; D005456:Fluorescent Dyes; D016257:Fura-2; D007295:Inositol Phosphates / Q000378:metabolism*; D017136:Ion Transport / Q000187:drug effects; D007811:Lanthanum / Q000494:pharmacology; D008345:Manganese / Q000494:pharmacology; D051381:Rats
D002021:Buffers; D004768:Enterotoxins; D005456:Fluorescent Dyes; D007295:Inositol Phosphates; C037420:stN protein, Vibrio cholerae; C028521:lanthanum chloride; C070379:1,2-bis(2-aminophenoxy)ethane N,N,N',N'-tetraacetic acid acetoxymethyl ester; D008345:Manganese; D004533:Egtazic Acid; D007811:Lanthanum; D003620:Dantrolene; D002118:Calcium; D016257:Fura-2