| Effects of muscarinic receptor stimulation on the thyrotropin-induced thyroxine release in the guinea pig thyroid |
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Hong-hyun Kim, Jin-shang Kim |
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College of Veterinary Medicine, Chonbuk National University |
| 기니픽 갑상선에서 Thyrotropin에 의한 thyroxine 유리에 대한 muscarinic 수용체 자극효과 |
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김홍현, 김진상 |
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전북대학교 수의과대학 |
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| Abstract |
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The present experiments were performed to examine the effects of acetylcholine (ACh) and carbachol (CC) on thyroxine ($T_4$) release and any possible relation between inhibition of $T_4$ release and signaling pathway in guinea pig thyroids. The thyroids were incubated in the medium containing the test agents, samples of the medium were assayed for $T_4$ by EIA kits. ACh and CC inhibited the TSH-stimulated $T_4$ release. These inhibition were reversed by atropine, but not by d-tubocurarine. The inhibitory effects of ACh on $T_4$ release were prevented by $M_{1^-}$ and $M_{3^-}$muscarinic antagonists and its inhibition was also slightly reversed by $M_{2^-}$ and $M_{4^-}$muscarinic antagonists. R59022, like ACh and CC, also inhibited the TSH-stimulated $T_4$ release. This inhibition was reversed by protein kinase C inhibitor and $Ca^{2+}$ channel blocker. The present study suggests that cholinergic inhibition of $T_4$ release from thyroids can be induced mainly by activation of the $M_{1^-}$ or $M_{3^-}$ receptors and that it is mediated through the muscarinic receptorstimulated protein kinase C activation. |
| Key Words:
muscarinic receptor, thyroxine, thyroid, protein kinase C, acetylcholine |
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