β-Endorphin分泌に対するCholera toxinの影響:下垂体中葉遊離細胞における検討

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The intermediate lobe cells of pituitary gland synthesize and secrete bioactive peptides derived from proopiomelanocortin. In the present study, we investigated the effects of cholera toxin on the release of β-endorphin (β-Ep) from dispersed-intermediate lobe cells of rats. Cholera toxin added into culture medium, enhanced the intracellular accumulation of adenosine 3', 5'-monophosphate (cAMP) and the release of β-endorphin like immunoreactive substance (β-END-LIS). A positive dose-response relationship existed between the concentration of cholera toxin and the release of j3-END-LIS or the accumulation of cAMP. Maximal response was obtained with approximately 3 × 10-10M (in β-END-LIS release) and 1 × 10-9M (in cAMP accumulation) concentration of cholera toxin. Incubation with cholera toxin (3 × 10-8M) resulted in a significant rise of cAMP accumulation after 20-30 min, and a 2-2.5 fold increase of β-END-LIS release occurred after 60 min in comparison with nontreated cells. cAMP analog and phosphodiesterase inhibitor also increased the β-END-LIS release10). These results suggested the close relationship between cAMP accumulation and its biological effect (i.e. β-END-LIS release).
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