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This Article Full Text Full Text (PDF) All Versions of this Article: 285/5/E1039    most recent 00238.2003v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via ISI Web of Science (1) Citing Articles via Google Scholar Google Scholar Articles by Vazquez-Martinez, R. Articles by Malagon, M. M. Search for Related Content PubMed PubMed Citation Articles by Vazquez-Martinez, R. Articles by Malagon, M. M.

Melanotrope secretory cycle is regulated by physiological inputs via the hypothalamus

¹Department of Cell Biology, University of Cordoba, 14014-Cordoba, Spain; and ²European Institute for Peptide Research (IFRMP 23), Laboratory of Cellular and Molecular Neuroendocrinology, Institut National de la Santé et de la Recherche Médicale U413, Unité Associée Centre National de la Recherche Scientifique, University of Rouen, 76821 Mont-Saint-Aignan, France

Submitted 23 May 2003 ; accepted in final form 16 July 2003

Previously, it has been shown that background color conditions regulate the overall activity of the frog intermediate lobe by varying the proportions of the two subtypes of melanotropes existing in the gland, the highly active or secretory melanotropes and hormone storage melanotropes, depending on melanocyte-stimulating hormone requirements. However, the factors and mechanisms underlying these background-induced changes are still unknown. In the present study, we investigated whether hypothalamic factors known to regulate melanotrope cell function can induce changes in vitro similar to those caused by background adaptation in vivo. We found that the inhibitors apomorphine (a dopamine receptor agonist) and neuropeptide Y decreased the number of active melanotropes and increased simultaneously that of storage melanotropes. On the other hand, the stimulator TRH increased the number of active cells and concomitantly reduced that of storage cells. Inasmuch as none of these treatments modified the apoptotic and proliferation rates in melanotrope cells, it appears that these hypothalamic factors caused actual interconversions of cells from a subpopulation to its counterpart. Taken together, these findings suggest that the hypothalamus would control melanotrope activity not only through short-term regulation of hormone synthesis and release, but also through a long-term regulation of the secretory phenotype of these cells whereby the activity of the intermediate lobe would be adjusted to fulfill the hormonal requirements imposed by background conditions.

dopamine; melanotrope cell heterogeneity; neuropeptide Y; secretory cycle; thyrotropin-releasing hormone