Authors: M J Perone A N Chisari C L Gómez Dumm E Spinedi F E Estivariz
Publish Date: 2014/03/27
Volume: 20, Issue: 4, Pages: 172-182
Abstract
The aim of the present study was to elucidate the modulatory effect of transient changes in endogenous glucocorticoids occurring after bilateral adrenal enucleation ENUC on anterior pituitary AP proopiomelanocortin POMCderived peptides synthesis and output in rats For this purpose adult female rats were either bilaterally ENUC adrenalelectomized ADX or shamoperated SHAM and killed by decapitation 2 7 14 and 21 days after surgery Trunk blood was collected for measurements of ACTH βendorphin βEND and corticosterone B concentrations APs were quickly dissected for the determination of ACTH βendorphin βENDlike βENDLI and γ3MSH contents and adrenal glands were removed and submitted to histological study The results indicate that ENUC and ADX increased AP POMCrelated peptides synthesis and release in association with changes in the AP processing of peptides belonging to the Nterminal γ3MSH mid ACTH and Cterminal βLPH/ENDs portions of POMC While ADX abolished plasma B levels ENUC induced a transient day 2 decrease in plasma B concentrations which returned to SHAM levels at 7 days after surgery These data tallied with the histological observations carried out indicating a timedependent regenerative process of the adrenal which was completed by three weeks after ENUC There was a different pattern in plasma ACTH and βEND levels between ENUC and ADX maximal plasma peptide levels were found 7–14 days after ENUC then falling down to SHAM values at 21 days post ENUC Conversely there was a constant increment in plasma peptide levels up to 21 days after ADX At 2 days after both ENUC and ADX all peptides measured in the AP were lower than SHAM values thus reflecting a rapid corticotrope secretion Thereafter 7 or more days after surgery AP peptide content in ADX rats increased in a timerelated fashion up to 21 days after surgery Only βENDLI showed a similar AP content to that of the SHAM group thereafter indicating a preferential cleavage of POMC to βEND long after ADX 21 days ENUC rats showed increased AP POMC peptides content throughout the whole time and it was significantly different from SHAM and ADX values 14 days postsurgery Interestingly we found an increment in AP γ3MSH a peptide which is preferentially synthesized in the intermediate lobe of the rat pituitary in both ENUC and ADX situations Our results further indicate that 1 glucocorticoids from regenerating adrenal origin induce a fast negative feedback mechanism on AP secretion and 2 there might be a delayed inhibitory action of newly synthesized corticosteroids on higher levels of the central nervous system The lack of glucocorticoids ADX clearly corroborates a persistent enhancement of AP POMCrelated peptides synthesis and secretion The differences in AP processing of POMC between ENUC and ADX might be due to qualitative/quantitative changes in hypotalamic ACTH secretagogues output
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