AJP - Endocrinology and Metabolism, Vol 269, Issue 3 E451-E457, Copyright © 1995 by American Physiological Society
Tumor-related selection of calcium signals in vasopressin-stimulated human adenomatous corticotrophs
J. B. Corcuff, N. C. Guerineau, A. Tabarin and P. Mollard
Laboratory of Neurophysiology, Universite de Bordeaux II, France.
The action of arginine vasopressin (AVP) on cytosolic free calcium
concentration ([Ca2+]i) was studied at the single-cell level in
corticotrophs cultured from pituitary adenoma fragments removed from eight
patients with Cushing's disease. AVP evoked distinct [Ca2+]i responses with
regard to the tumor origin. In cells from two tumors, AVP consistently
evoked a series of characteristic elevations of [Ca2+]i (transient pattern)
that depended on Ca2+ entry. In cells from the other tumors, AVP triggered
different patterns of [Ca2+]i rise, which consisted of low-amplitude slow
monophasic increases at low AVP concentration and a high-amplitude spike
increase followed by a sustained plateau (spike-plateau pattern) at higher
concentration of AVP. Slow monophasic increases and the spike of
spike-plateau responses were due to calcium release from internal stores,
whereas the plateau was a consequence of calcium entry. These two patterns
(transient vs. spike-plateau) resemble those observed in subpopulations of
corticotrophs from healthy rat pituitary glands (Corcuff et al., J. Biol.
Chem. 268: 22313-22321, 1993), suggesting that tumorigenesis can lead in
pituitary tissues to a selection rather than alteration of AVP [Ca2+]i
signals.
