Kelly L A, Butcher R W
Metabolism. 1975 Mar;24(3):359-68. doi: 10.1016/0026-0495(75)90116-x.
Cultured human epidermoid carcinoma (HEp-2) cells were found to contain a highly responsive, catecholamine-sensitive adenyl cyclase activity in cellfree preparations. By contrast, cyclic AMP levels in intact HEp-2 cells were at best only marginally increased by catecholamines under a variety of conditions. The lack of an intact cell response could not be accounted for by escape of cyclic AMP to the medium, excessive phosphodiesterase activity, inactivation of the catecholamine, or by unusual kinetics of the system. However, in the presence of 1-methyl,3-iso-butylxanthine (MIX), a potent phosphodiesterase inhibitor, a moderate catecholamine response was observed in the intact cells. A significant elevation of cyclic AMP levels in the presence of MIX was observed at 0.3 muM epinephrine, and maximal levels occurred at 10 muM. Norepinephrine was much less effective than either epinephrine or isopropylnorepinephrine at 10 muM concentrations. In addition, intact cells slowly but steadily released cyclic AMP into the incubation medium over the course of 60-min incubations in the presence of MIX and epinephrine; maximum intracellular levels were reached by 5 min.
在无细胞制剂中发现培养的人表皮样癌（HEp - 2）细胞含有高度敏感的、儿茶酚胺敏感的腺苷酸环化酶活性。相比之下，在多种条件下，儿茶酚胺对完整的HEp - 2细胞中环状AMP水平的升高作用微乎其微。完整细胞缺乏反应不能归因于环状AMP逸出到培养基中、磷酸二酯酶活性过高、儿茶酚胺失活或该系统异常的动力学。然而，在存在强效磷酸二酯酶抑制剂1 - 甲基 - 3 - 异丁基黄嘌呤（MIX）的情况下，在完整细胞中观察到适度的儿茶酚胺反应。在0.3μM肾上腺素存在下，观察到MIX存在时环状AMP水平显著升高，最大水平出现在10μM时。在10μM浓度下，去甲肾上腺素的效果远不如肾上腺素或异丙基去甲肾上腺素。此外，在MIX和肾上腺素存在下，完整细胞在60分钟的孵育过程中缓慢但稳定地将环状AMP释放到孵育培养基中；5分钟时达到最大细胞内水平。
