Brown E M, Hurwitz S H, Aurbach G D
Endocrinology. 1978 Sep;103(3):893-9. doi: 10.1210/endo-103-3-893.
The possibility of alpha-adrenergic modulation of cAMP accumulation and parathyroid hormone (PTH) release was investigated in dispersed bovine parathyroid cells. cAMP accumulation due to the mixed alpha- and beta-adrenergic agonists, (-)epinephrine and (-)norepinephrine, was significantly enhanced by the alpha-adrenergic inhibitor phentolamine; that due to the "pure" beta-adrenergic agonist, (-)isoproterenol, was not altered significantly. Direct inhibition of agonist-stimulated cAMP accumulation was effected by adding increasing concentrations of (-)epinephrine to concentrations of (-)isoproterenol maximally stimulating cAMP accumulation. A 50-75% inhibition of cAMP was observed which was specifically blocked by phentolamine. This inhibition was not specific for beta-adrenergic stimulation, as (-)epinephrine also inhibited dopamine-stimulated cAMP accumulation. The inhibition of (-)isoproterenol-stimulated cAMP accumulation by (-)epinephrine was unaffected by ambient calcium concentration. Stimulation of PTH release by (-)epinephrine and (-)norepinephrine was potentiated by phentolamine and inhibited by the beta-adrenergic blocker, (-)propranolol, demonstrating alpha-adrenergic modulation of hormone release and confirming the close relationship between cAMP accumulation and PTH release previously shown in this system. These results demonstrate the presence of an alpha-adrenergic receptor in dispersed bovine parathyroid cells which inhibits agonist-stimulated cAMP accumulation and PTH release by a mechanism independent of extracellular calcium.
在分散的牛甲状旁腺细胞中研究了α-肾上腺素能调节环磷酸腺苷（cAMP）积累和甲状旁腺激素（PTH）释放的可能性。由α-和β-肾上腺素能混合激动剂（-）肾上腺素和（-）去甲肾上腺素引起的cAMP积累，被α-肾上腺素能抑制剂酚妥拉明显著增强；而由“纯”β-肾上腺素能激动剂（-）异丙肾上腺素引起的cAMP积累则无显著变化。通过向最大刺激cAMP积累的（-）异丙肾上腺素浓度中添加递增浓度的（-）肾上腺素，实现了对激动剂刺激的cAMP积累的直接抑制。观察到cAMP有50 - 75%的抑制，且该抑制被酚妥拉明特异性阻断。这种抑制并非β-肾上腺素能刺激所特有，因为（-）肾上腺素也抑制多巴胺刺激的cAMP积累。（-）肾上腺素对（-）异丙肾上腺素刺激的cAMP积累的抑制不受细胞外钙浓度的影响。（-）肾上腺素和（-）去甲肾上腺素对PTH释放的刺激被酚妥拉明增强，被β-肾上腺素能阻滞剂（-）普萘洛尔抑制，这表明激素释放存在α-肾上腺素能调节，并证实了此前在该系统中所显示的cAMP积累与PTH释放之间的密切关系。这些结果表明，在分散的牛甲状旁腺细胞中存在一种α-肾上腺素能受体，它通过一种独立于细胞外钙的机制抑制激动剂刺激的cAMP积累和PTH释放。
