Click here to close
Hello! We notice that you are using Internet Explorer, which is not supported by Xenbase and may cause the site to display incorrectly.
We suggest using a current version of Chrome,
FireFox, or Safari.
???displayArticle.abstract???
The secretion of alpha-melanophore-stimulating hormone (alpha-MSH) from melanotrope cells in the pituitary gland of Xenopus laevis is regulated by various neural factors, both classical neurotransmitters and neuropeptides. The majority of these cells (80%) display spontaneous Ca2+ oscillations. In order to gain a better understanding of the external regulation of intracellular Ca2+ ([Ca2+]i) in the melanotrope cell, we have examined the action of well known alpha-MSH secretagogues on the Ca2+ oscillations. It is shown that all secretagogues tested also control the oscillatory state of Xenopus melanotropes, that is, the secreto-inhibitors dopamine, isoguvacine (gamma-aminobutyric acid, GABAA agonist), baclofen (GABAB agonist) and neuropeptide Y evoked a rapid quenching of the spontaneous Ca2+ oscillations, whereas the secreto-stimulant sauvagine, an amphibian peptide related to corticotropin releasing hormone, induced oscillatory activity in non-oscillating cells. Supporting argument is given for the idea that the regulation of Ca2+ oscillations is a focal point in the regulation of secretory activity of melanotrope cells. There was considerable heterogeneity among melanotrope cells in the threshold of their Ca2+ response to secretagogue treatment. This heterogeneity may be the basis for melanotrope cell recruitment observed during physiological adaptations of the animal to the light intensity of its background.
Arita,
Identification by the sequential cell immunoblot assay of a subpopulation of rat dopamine-unresponsive lactotrophs.
1991, Pubmed
Arita,
Identification by the sequential cell immunoblot assay of a subpopulation of rat dopamine-unresponsive lactotrophs.
1991,
Pubmed
de Koning,
Dynamics of cyclic-AMP efflux in relation to alpha-MSH secretion from melanotrope cells of Xenopus laevis.
1992,
Pubmed
,
Xenbase
de Koning,
Indirect action of elevated potassium and neuropeptide Y on alpha MSH secretion from the pars intermedia of Xenopus laevis: a biochemical and morphological study.
1991,
Pubmed
,
Xenbase
de Rijk,
Morphology of the pars intermedia and the melanophore-stimulating cells in Xenopus laevis in relation to background adaptation.
1990,
Pubmed
,
Xenbase
De Rijk,
[125I]Bolton-Hunter neuropeptide-Y-binding sites on folliculo-stellate cells of the pars intermedia of Xenopus laevis: a combined autoradiographic and immunocytochemical study.
1991,
Pubmed
,
Xenbase
Desrues,
Thyrotrophin-releasing hormone stimulates polyphosphoinositide metabolism in the frog neurointermediate lobe.
1990,
Pubmed
Holl,
Intracellular calcium concentration and growth hormone secretion in individual somatotropes: effects of growth hormone-releasing factor and somatostatin.
1988,
Pubmed
Iida,
Spontaneous and agonist-induced calcium oscillations in pituitary gonadotrophs.
1991,
Pubmed
Ince,
A teflon culture dish for high-magnification microscopy and measurements in single cells.
1985,
Pubmed
Jenks,
Dual action of GABAA receptors on the secretory process of melanotrophs of Xenopus laevis.
1993,
Pubmed
,
Xenbase
Kongsamut,
Melanotrophs of Xenopus laevis do respond directly to neuropeptide-Y as evidenced by reductions in secretion and cytosolic calcium pulsing in isolated cells.
1993,
Pubmed
,
Xenbase
Law,
Ability of repetitive Ca2+ spikes to stimulate prolactin release is frequency dependent.
1989,
Pubmed
Leenders,
Differential effects of coexisting dopamine, GABA and NPY on alpha-MSH secretion from melanotrope cells of Xenopus laevis.
1993,
Pubmed
,
Xenbase
Leong,
A potential code of luteinizing hormone-releasing hormone-induced calcium ion responses in the regulation of luteinizing hormone secretion among individual gonadotropes.
1991,
Pubmed
Luque,
Subpopulations of lactotropes detected with the reverse hemolytic plaque assay show differential responsiveness to dopamine.
1986,
Pubmed
Neylon,
Spatial dynamics of intracellular calcium in agonist-stimulated vascular smooth muscle cells.
1990,
Pubmed
Nitschke,
Antidiuretic hormone acts via V1 receptors on intracellular calcium in the isolated perfused rabbit cortical thick ascending limb.
1991,
Pubmed
Poenie,
Calcium rises abruptly and briefly throughout the cell at the onset of anaphase.
1986,
Pubmed
Scheenen,
Spontaneous calcium oscillations in Xenopus laevis melanotrope cells are mediated by omega-conotoxin sensitive calcium channels.
1994,
Pubmed
,
Xenbase
Shibuya,
Spontaneous cytosolic calcium pulsing detected in Xenopus melanotrophs: modulation by secreto-inhibitory and stimulant ligands.
1993,
Pubmed
,
Xenbase
Shibuya,
Effectiveness of GABAB antagonists in inhibiting baclofen-induced reductions in cytosolic free Ca concentration in isolated melanotrophs of rat.
1992,
Pubmed
Shibuya,
Spontaneous cytosolic calcium pulses in Xenopus melanotrophs are due to calcium influx during phasic increases in the calcium permeability of the cell membrane.
1993,
Pubmed
,
Xenbase
Valentijn,
Involvement of non-selective cationic channels in the generation of pacemaker depolarizations and firing behaviour in cultured frog melanotrophs.
1991,
Pubmed
Verburg-van Kemenade,
Characterization of gamma-aminobutyric acid receptors in the neurointermediate lobe of the amphibian Xenopus laevis.
1987,
Pubmed
,
Xenbase
Verburg-van Kemenade,
Assessment of TRH as a potential MSH release stimulating factor in Xenopus laevis.
1987,
Pubmed
,
Xenbase
Verburg-Van Kemenade,
Characteristics of receptors for dopamine in the pars intermedia of the amphibian Xenopus laevis.
1986,
Pubmed
,
Xenbase
Verburg-Van Kemenade,
Regulation of MSH release from the neurointermediate lobe of Xenopus laevis by CRF-like peptides.
1987,
Pubmed
,
Xenbase
Verburg-Van Kemenade,
GABA and dopamine act directly on melanotropes of Xenopus to inhibit MSH secretion.
1986,
Pubmed
,
Xenbase
