Authors: A Spada M Bassetti E Martino G Giannattasio P BeckPeccoz A Sartorio L Vallar L Baschieri A Pinchera G Faglia
Publish Date: 2014/04/02
Volume: 8, Issue: 3, Pages: 193-198
Abstract
We have studied the in vitro TSH secretion and the adenylate cyclase AC activity of a human pituitary adenoma surgically removed from a hyperthyroid patient showing high serum TSH levels The tumor appeared almost homogeneously constituted by cells positive for an antiTSHbeta antiserum and showing the ultrastructural characteristics of the adenomatous thyrotrophs Adenoma fragments released in vitro a large amount of TSH 1484 μU/mg prot/30 min alphasubunit355 ng/mg prot/30 min and TSHbeta 101 ng/mg prot/30 min The effects of somatostatin GHRIH and dopamine DA on the hormone release have been tested in vitro Both agents markedly inhibited the release of intact TSH and TSHbeta whereas the release of alphasubunit was less affected The two agents were effective at concentrations higher than 10−8M The ability of GHRIH and DA in modulating the AC activity was investigated in membrane fraction preparations GHRIH inhibited AC at concentrations higher than 10 −7M The maximal inhibition was 32 at 10−5 M Conversely DA slightly stimulated AC activity This effects was not mimicked by the dopaminergic ergot CH 29–717 which was completely ineffective on the enzyme These results suggest that 1 in this TSHsecreting pituitary adenoma a normal secretory response to the inhibiting agents GHRIH and DA is present 2 different mechanisms of transduction of the GHRIH and DA signals cAMP dependent and cAMP independent could be operating in this tumor
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