Karaplis A C, Funk C D, Powell W S
Endocrine Laboratory, Royal Victoria Hospital, Montreal, Quebec, Canada.
Biochim Biophys Acta. 1989 Mar 6;1010(3):369-76. doi: 10.1016/0167-4889(89)90064-5.
We have previously shown that plasma membranes from adrenal medulla possess specific high-affinity binding sites for prostaglandins (PGs) E1 and E2. We have now investigated the binding of PGE2 to intact bovine adrenal chromaffin cells and the effects of prostaglandins on the release of catecholamines from these cells. Adrenal chromaffin cells specifically bound PGE2 with a dissociation constant of 2 nM and a concentration of about 40,000 binding sites per cell. Low concentrations of PGE2 inhibited the nicotine-stimulated release of catecholamines from these cells. The effect of PGE2 was biphasic, the maximal inhibitory effect being observed at a concentration of between 1 and 10 nM. Higher concentrations (1 microM) of PGE2 had minimal inhibitory effects on nicotine-evoked noradrenaline release, but instead had a direct stimulatory effect in the absence of cholinergic agonists. Although the stimulatory effects of high concentrations of PGE2 were reproducibly observed in all cell preparations, only about one-half of the cultures tested responded to the inhibitory effects of this prostaglandin. It is possible that PGE2 plays a modulatory role in the regulation of catecholamine secretion from the adrenal medulla.
我们之前已经表明，肾上腺髓质的质膜对前列腺素（PGs）E1和E2具有特定的高亲和力结合位点。我们现在研究了PGE2与完整牛肾上腺嗜铬细胞的结合以及前列腺素对这些细胞儿茶酚胺释放的影响。肾上腺嗜铬细胞特异性结合PGE2，解离常数为2 nM，每个细胞约有40,000个结合位点。低浓度的PGE2抑制了尼古丁刺激的这些细胞儿茶酚胺释放。PGE2的作用是双相的，在1至10 nM的浓度下观察到最大抑制作用。较高浓度（1 microM）的PGE2对尼古丁诱发的去甲肾上腺素释放具有最小的抑制作用，但在没有胆碱能激动剂的情况下反而具有直接刺激作用。尽管在所有细胞制剂中都可重复观察到高浓度PGE2的刺激作用，但只有约一半的测试培养物对这种前列腺素的抑制作用有反应。PGE2可能在肾上腺髓质儿茶酚胺分泌的调节中起调节作用。
