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Dopaminergic Receptors in Human Prolactin-Secreting Adenomas: A Quantitative Study*

1980; Oxford University Press; Volume: 51; Issue: 5 Linguagem: Inglês

10.1210/jcem-51-5-1037

1945-7197

D. Bression, A. Brandi, Marie‐Pascale Martres, A. NOUSBAUM, F. Cesselin, J Racadot, F Peillon,

Estrogen and related hormone effects

Dopaminergic receptors were observed on the membranes of 26 human PRL-secreting adenomas. Two binding sites were found for [3H]domperidone, a selective dopamine antagonist, with a Kd1 of 0.29 ± 0.06 nM and a Kd2 of 4.19 ± 0.7 nM (n = 5). Bmax1 and Bmax2 (maximum numbers of binding sites, first and second sites, respectively) varied from one adenoma to another. When considering Bmax1, two different categories of PRL-secreting adenomas were distinguished, one with a concentration of receptor over 250 fmol/mg protein and others with lower concentrations of receptor (<250 fmol/mg protein). In the latter, when considering the volume of the tumor, a higher plasma PRL level was found. Two binding sites for [3H]domperidone also were found in the normal human hypophysis with Kd values similar to those of the adenomas (0.18 ± 0.04 and 3.95 ± 0.35 nM). The same number of binding sites was observed in normal pituitaries and in PRL-secreting adenomas. However, when considering the density of PRL-secreting cells in the two different tissues (prolactinomas contain 2 or 3 times more PRL-secreting cells than human pituitary tissue), one may suspect a defect in the dopaminergic inhibiting control in PRL-secreting adenomas.