Age-related alterations in prolactin binding sites in the female rat


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Age-related alterations in prolactin binding sites in the female rat
Acta Endocrinologica
Schneiter  P., Reymond  M. J., Lemarchand-Beraud  T.
0001-5598 (Print)
Statut éditorial
Date de publication
Journal Article
Research Support, Non-U.S. Gov't --- Old month value: Mar
Aging is associated with various neuroendocrine alterations, including in the rat a hypersecretion of PRL with maintained ovulations (repetitive pseudo-pregnancy) and a reduced activity of the hypothalamic dopaminergic neurons with loss of the neuron responsiveness to PRL, suggestive of age-related alterations in PRL receptors. In this study we have investigated PRL binding sites in the hypothalamus as well as in the mammary glands, the ovaries and the liver of young and old nulliparous female rats. The old rats (26-28 months) displayed spontaneous repetitive pseudopregnancies and they were compared with young (4-6 months) pseudopregnant rats; the binding studies were performed by saturation analysis using 125I-oPRL as ligand and particulate membrane preparations. In the hypothalamus, a negligible binding of PRL was observed in all fragments studied, mediobasal hypothalamus, median eminence, in both young and old rats and no characterization of the binding sites could be achieved. In the mammary glands, the number of PRL binding sites was appreciable in spite of the nulliparity of the rats, but it was smaller in the old than in the young rats (9.0 +/- 1.4 vs 14.9 +/- 1.2 fmol/mg protein; mean +/- SEM; p less than 0.02). In the ovaries, the density of PRL binding sites was similar in the old and young rats (112.6 +/- 9.7 vs 115.0 +/- 8.9 fmol/mg protein), illustrative of a maintained luteotropic effect of PRL with age in the rat. In contrast, in the liver a greater number of binding sites was found in the old than in the young rats (261.9 +/- 36.6 vs 63.6 +/- 5.8 fmol/mg protein; p less than 0.001), supportive of the ability of PRL to induce its own receptors in that tissue. The affinity constant of PRL binding was not altered with age in the tissues studied. These results are illustrative of tissue-specific modifications in the number of PRL binding sites with age and they are suggestive of a sustained biological activity of PRL in the old rats.
Aging/*metabolism Animals Binding Sites Female Follicle Stimulating Hormone/blood Hypothalamus/metabolism Liver/metabolism Luteinizing Hormone/blood Mammary Glands, Animal/metabolism Ovary/metabolism Progesterone/blood Prolactin/*metabolism Pseudopregnancy Rats Receptors, Prolactin/*metabolism
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Création de la notice
24/01/2008 14:31
Dernière modification de la notice
03/03/2018 18:24
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