Abstract
Immunoreactive insulin levels (IRI) were measured by a homologous fish insulin radioimmunoassay. An in vitro pancreatic islet superfusion technique was employed to monitor the changes in IRI in the presence and absence of specific adrenergic agonists and antagonists. Exogenous adrenaline at low concentrations (10 −10 M) inhibited IRI release but evoked an IRI stimulation at high concentrations (10 −10 M). The stimulation of IRI by adrenaline is thought to involve β-adrenoceptors located postsynaptically on the β-cell membrane as the effect of adrenaline was mimicked by the β-agonist, isoproterenol, and abolished by the β-antagonist propranolol. Phentolamine (an α-antagonist) potentiated the adrenergic stimulation of IRI, whereas yohimbine (an α 2-antagonist) was without effect. Phenylephrine ( α 1-adrenoceptor agonist) IRI release suggesting the presence of α 2-inhibitory adrenoceptors which exert a modulatory influence on adrenaline-stimulated insulin release.
Published Version
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