Differential transduction of dopamine signal in different subtypes of human growth hormone-secreting adenomas

Anna Spada, Monique Bassetti, Farzin Reza-Elahi, Maura Arosio, Paloma Gil-Del-Alamo, Lucia Vallar

Research output: Contribution to journalArticlepeer-review

Abstract

This article reports the effect of dopamine (DA) on adenylyl cyclase (AC) activity and intracellular free calcium concentration ([Ca2+]i) in 20 GH-secreting pituitary adenomas exclusively composed of somatotrophs (GH-omas) and 3 tumors largely constituted by mammosomatotrophs (MS-omas). DA (between 10 nmol/L and 100 μmol/L) did not reduce AC activity in any GH-omas, whereas the amine caused a significant inhibition in membranes from all MS-omas. The effect was detectable at DA concentrations higher than 0.1 μmol/L, and maximal inhibition (ranging from 24-30%) was reached at 10 μmol/L. The ergot derivative CH 29717 and l-sulpiride demonstrated potent agonist and antagonist activities, respectively. Somatostatin reduced AC activity in all tumors; the percent inhibition values (between 17-34%) were similar in GH-omas and MS-omas. In both GH-omas and MS-omas, DA (1 μmol/L) caused a significant [Ca2+]i reduction (between 17-44%) that was essentially due to the block of Ca2+influx from the extracellular spaces. The receptors involved in this effect showed the pharmacological properties of D2 receptors. In conclusion, the DA effect in tumoral somatotrophs is defective; DA fails to exert an inhibitory action on AC activity. In mammosomatotrophs, the typical D2 receptor-effector coupling is retained, resulting in decreased AC activity in these cells.

Original languageEnglish
Pages (from-to)411-417
Number of pages7
JournalJournal of Clinical Endocrinology and Metabolism
Volume78
Issue number2
DOIs
Publication statusPublished - 1994

ASJC Scopus subject areas

  • Endocrinology, Diabetes and Metabolism
  • Biochemistry
  • Endocrinology
  • Clinical Biochemistry
  • Biochemistry, medical

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