The effects of maitotoxin on 45Ca2+ flux and hormone release in GH3 rat pituitary cells.
Maitotoxin has been reported to activate calcium channels and stimulate calcium-dependent functions in several tissues, but a thorough investigation of 45Ca2+ fluxes is lacking. To characterize the influence of maitotoxin on 45Ca2+ flux in greater detail, we incubated dispersed GH3 pituitary tumor cells in 45Ca2+ with maitotoxin and other agents affecting calcium channels. Within 10 sec of exposure, maitotoxin induced a net calcium influx in cells at isotopic equilibrium. Calcium uptake was concentration dependent between 0.4 and 40 ng/ml maitotoxin and was inhibited by antagonists of voltage-dependent calcium channels but not by inhibitors of sodium channels. PRL and GH release from perifused GH3 cells was stimulated within 1 min by maitotoxin. We conclude that maitotoxin causes a rapid, concentration-dependent influx of calcium through presumed voltage-dependent endogenous calcium channels, culminating in enhanced hormone release. This potent toxin may provide a more precise understanding of the role of calcium in the stimulus-secretion coupling process.
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I S
IS
Judd
A M
AM
Cronin
M J
MJ
Koike
K
K
Schettini
G
G
Yasumoto
T
T
MacLeod
R M
RM
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002460:Cell Line; D005711:Gallopamil / Q000494:pharmacology; D013006:Growth Hormone / Q000378:metabolism*; D007473:Ion Channels / Q000378:metabolism; D008345:Manganese / Q000494:pharmacology; D008387:Marine Toxins / Q000494:pharmacology*; D009543:Nifedipine / Q000494:pharmacology; D035964:Oxocins; D010902:Pituitary Gland / Q000187:drug effects; D010911:Pituitary Neoplasms / Q000378:metabolism*; D011188:Potassium / Q000494:pharmacology; D011388:Prolactin / Q000378:metabolism*; D051381:Rats; D013997:Time Factors; D000095702:Polyether Toxins
D002118:Calcium; D005711:Gallopamil; D013006:Growth Hormone; D007473:Ion Channels; D008345:Manganese; D008387:Marine Toxins; D009543:Nifedipine; D035964:Oxocins; D011188:Potassium; D011388:Prolactin; C020394:maitotoxin; D000095702:Polyether Toxins