This article reports the effect of dopamine (DA) on adenylyl cyclase (AC) activity and intracellular free calcium concentrations ([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.

Differential transduction of dopamine signal in different subtypes of human growth hormone-secreting adenomas / A. Spada A, M. Bassetti, F. Reza-Elahi, M. Arosio, P. Gil-del-Alamo. L. Vallar. - In: THE JOURNAL OF CLINICAL ENDOCRINOLOGY AND METABOLISM. - ISSN 0021-972X. - 78:2(1994), pp. 411-417.

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

A. Spada A;M. Arosio
Penultimo
;
P. Gil-del-Alamo. L. Vallar
1994

Abstract

This article reports the effect of dopamine (DA) on adenylyl cyclase (AC) activity and intracellular free calcium concentrations ([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.
Dopamine; signal transduction; growth hormone-secreting adenomas
Settore BIO/14 - Farmacologia
Settore MED/13 - Endocrinologia
1994
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2434/201811
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