AJP - Endocrinology and Metabolism, Vol 272, Issue 2 E282-E287, Copyright © 1997 by American Physiological Society

ARTICLES

Phenotypic characterization and functional correlation of alpha-MSH binding to pituitary cells

T. Zheng, C. Villalobos, K. D. Nusser, T. W. Gettys, W. J. Faught, J. P. Castano and L. S. Frawley
Department of Cell Biology and Anatomy, Medical University of South Carolina, Charleston 29425, USA.

It is clear that alpha-melanocyte-stimulating hormone (alpha-MSH), released by the hypophysial neurointermediate lobe, is a mediator of suckling-induced prolactin release, but several questions surrounding its role remain unresolved. Accordingly, the objectives of the present study were 1) to establish whether alpha-MSH could bind in a reversible manner to a specific secretory type cell within the adenohypophysis (AP), 2) to resolve the issue of whether the peptide could compete with dopamine for the same receptor binding site, and 3) to seek a functional signaling correlate for alpha-MSH binding. In pursuit of these objectives, we subjected pituitary cells from lactating rats to alpha-MSH receptor autoradiography, AP hormone immunocytochemistry, or digital imaging fluorescence microscopy with fura 2 as a calcium-sensitive probe. Our results show that alpha-MSH binding is restricted to mammotropes and that a specific subpopulation of these express functional alpha-MSH receptors that are coupled to a Ca2+ signaling pathway. Moreover, alpha-MSH does not compete with dopamine antagonists/agonists for the same binding site.

This article has been cited by other articles:

				M. E. Freeman, B. Kanyicska, A. Lerant, and G. Nagy Prolactin: Structure, Function, and Regulation of Secretion Physiol Rev, October 1, 2000; 80(4): 1523 - 1631. [Abstract] [Full Text] [PDF]

				L. Nunez and L. S. Frawley alpha -MSH potentiates the responsiveness of mammotropes by increasing Ca2+ entry Am J Physiol Endocrinol Metab, June 1, 1998; 274(6): E971 - E977. [Abstract] [Full Text] [PDF]