[3H]Spiperone binding to human anterior pituitaries and pituitary adenomas secreting prolactin, growth hormone, and adrenocorticotropic hormone

M. J. Cronin, C. Y. Cheung, C. B. Wilson

Research output: Research - peer-reviewArticle

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Abstract

Dopamine or its agonists inhibit PRL release from the anterior pituitary both in vivo and in vitro, while specific dopaminergic antagonists can reverse this inhibition. The direct measurement of dopamine in portal blood and dopamine receptors in the anterior pituitary of the rat, sheep, and steer with radioligand-binding assays supports the hypothesis that dopamine is a PRL inhibitory factor. In the present study, [3H]spiperone (a dopamine antagonist) bound to an apparent single class of high affinity sites in human anterior pituitaries as well as in human PRL-secreting pituitary adenomas. Neither the dissociation constant [K(d) = 2.2 ± 0.7 and 3.1 ± 1.4 nM, respectively (mean ± SEM)] nor the site numbers per PRL content were different in these two tissues. However, if the site numbers were expressed per mg protein, there were significantly more sites in the PRL-secreting pituitary adenomas (707 ± 113 fm/mg protein; n = 5) than in the control anterior pituitaries (141 ± 22 fm/mg protein; n = 7). This may be due to an increased density of mammotrophs and, thus, an increased number of binding sites in the adenomas. The development of PRL-secreting pituitary adenomas is probably not due to the absence of dopamine receptors or a decrease in their affinity for [3H]spiperone. There was undetectable binding in two of four experiments with GH-secreting adenomas and in two with ACTH-producing adenomas. In the other two experiments with GH-secreting adenomas, site numbers similar to the control anterior pituitaries were observed.

LanguageEnglish (US)
Pages387-391
Number of pages5
JournalJournal of Clinical Endocrinology and Metabolism
Volume50
Issue number2
StatePublished - 1980
Externally publishedYes

Fingerprint

Spiperone
Prolactin
Adrenocorticotropic Hormone
Growth Hormone
Dopamine
Proteins
Growth Hormone-Secreting Pituitary Adenoma
Adenoma
Prolactinoma
Dopamine Antagonists
Dopamine Receptors
Experiments
Rats
Assays
Blood
Binding Sites
Tissue
Scanning electron microscopy
Radioligand Assay
Sheep

ASJC Scopus subject areas

  • Biochemistry
  • Endocrinology, Diabetes and Metabolism

Cite this

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abstract = "Dopamine or its agonists inhibit PRL release from the anterior pituitary both in vivo and in vitro, while specific dopaminergic antagonists can reverse this inhibition. The direct measurement of dopamine in portal blood and dopamine receptors in the anterior pituitary of the rat, sheep, and steer with radioligand-binding assays supports the hypothesis that dopamine is a PRL inhibitory factor. In the present study, [3H]spiperone (a dopamine antagonist) bound to an apparent single class of high affinity sites in human anterior pituitaries as well as in human PRL-secreting pituitary adenomas. Neither the dissociation constant [K(d) = 2.2 ± 0.7 and 3.1 ± 1.4 nM, respectively (mean ± SEM)] nor the site numbers per PRL content were different in these two tissues. However, if the site numbers were expressed per mg protein, there were significantly more sites in the PRL-secreting pituitary adenomas (707 ± 113 fm/mg protein; n = 5) than in the control anterior pituitaries (141 ± 22 fm/mg protein; n = 7). This may be due to an increased density of mammotrophs and, thus, an increased number of binding sites in the adenomas. The development of PRL-secreting pituitary adenomas is probably not due to the absence of dopamine receptors or a decrease in their affinity for [3H]spiperone. There was undetectable binding in two of four experiments with GH-secreting adenomas and in two with ACTH-producing adenomas. In the other two experiments with GH-secreting adenomas, site numbers similar to the control anterior pituitaries were observed.",
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