AJP - Endocrinology and Metabolism, Vol 247, Issue 4 520-E525, Copyright © 1984 by American Physiological Society
Maitotoxin stimulates hormonal release and calcium flux in rat anterior pituitary cells in vitro
G. Schettini, K. Koike, I. S. Login, A. M. Judd, M. J. Cronin, T. Yasumoto and R. M. MacLeod
The marine dinoflagellate toxin maitotoxin (MTX), an activator of calcium
channels, stimulates the release of prolactin (PRL), growth hormone (GH),
thyroid-stimulating hormone (TSH), and luteinizing hormone (LH) from
monolayers of anterior pituitary cells in a dose-dependent manner.
Maitotoxin significantly increased PRL, GH, and LH release within 1.5 min
and TSH release within 3.5 min, and the stimulation continued for at least
1 h (P less than 0.01). MTX-stimulated hormonal release was blocked by the
calcium channel blocker manganese (P less than 0.01). In freshly dispersed
perifused pituitary cells in columns, exposure to MTX for 10 min markedly
increased PRL, GH, TSH, and LH release for at least 1 h after withdrawal of
the toxin. In other experiments, MTX significantly stimulated 45Ca2+
exchange by dispersed pituitary cells within 30 s, continuing for at least
30 min. We conclude that MTX increases anterior pituitary hormonal release,
possibly by activating calcium channels, thereby increasing cellular
calcium influx. Thus MTX may be a useful agent for investigating the
involvement of Ca2+ in hormonal secretory processes.
