Melatonin inhibits insulin secretion and decreases PKA levels without interfering with glucose metabolism in rat pancreatic islets.
J Pineal Res
; 33(3): 156-60, 2002 Oct.
Article
em En
| MEDLINE
| ID: mdl-12220330
The effect of melatonin (0.1 microM) on freshly isolated islets from adult rats was investigated. Melatonin caused a marked decrease of insulin secretion by islets in response to glucose. The mechanism involved was then examined. Melatonin did not interfere with glucose metabolism as indicated by the measurement of glucose oxidation. However, the content of the protein kinase A (PKA) catalytic alpha-subunit was significantly decreased in islets exposed to melatonin for 1 hr in the presence of 8.3 mM glucose, whereas that of the protein kinase C (PKC) alpha-subunit remained unchanged. Melatonin also inhibited forskolin-induced insulin secretion, a well known activator of adenylate cyclase (AC) activity. This may explain the low content of insulin found in islets incubated in the presence of melatonin for 3 hr. In fact, 3',5' -cyclic adenosine monophosphate (cAMP), a product of AC activity, stimulates insulin synthesis. These findings led us to postulate that a down-regulation of the PKA signaling pathway may be the mechanism involved in the melatonin inhibition of the process of glucose-induced insulin secretion.
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Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Ilhotas Pancreáticas
/
Proteínas Quinases Dependentes de AMP Cíclico
/
Insulina
/
Melatonina
Limite:
Animals
Idioma:
En
Revista:
J Pineal Res
Assunto da revista:
ENDOCRINOLOGIA
Ano de publicação:
2002
Tipo de documento:
Article
País de afiliação:
Brasil
País de publicação:
Reino Unido