Petit A, Gallo-Payet N, Lehoux J G, Bellabarba D, Bélisle S
Department of Obstetric and Gynecology, University of Montréal, Québec, Canada.
Life Sci. 1991;49(6):465-72. doi: 10.1016/0024-3205(91)90589-4.
We previously reported that kappa opiates stimulated the release of human placental lactogen (hPL) from human placental cells. In this study, we investigated the role of adenylate cyclase as a potential cellular mediator of such an effect. Incubations with ethylketocyclazocine (EKC) led to a time- and dose-dependent inhibition of adenylate cyclase activity. The maximal inhibition was 45 +/- 5% of control value after 15 min exposure to 10(-7)M EKC. This inhibition was reversed by opiate antagonist naloxone and was specific to kappa opiate type. Preincubation of human trophoblastic cells with 0.1 microgram/ml Islet-Activating-Protein (IAP; also called pertussis toxin) did not modify basal adenylate cyclase activity but abolished the inhibition of adenylate cyclase activity by EKC, indicating that the effect of opiates on cAMP production was mediated by an IAP-sensitive GTP binding protein. Also, IAP stimulated basal hPL release; the control levels were 22.4 ng/ml and 46.5 ng/ml without and with IAP respectively. However, the EKC-stimulated hPL levels were unchanged by preincubation with IAP. This difference in cAMP and hPL response in IAP-treated cells suggested that the opiate receptors are not directly coupled to adenylate cyclase. This hypothesis was confirmed by 1) experiments on placental membranes showing that in absence of the cytoplasmic elements (membranes only), EKC had no effect on membrane adenylate cyclase and 2) experiments on placental cells showing that dibutyryl-cAMP (dbcAMP) stimulated hPL release.
我们先前报道过，κ阿片类物质可刺激人胎盘细胞释放人胎盘催乳素（hPL）。在本研究中，我们调查了腺苷酸环化酶作为这种效应潜在细胞介质的作用。用乙基酮环唑新（EKC）孵育导致腺苷酸环化酶活性出现时间和剂量依赖性抑制。暴露于10⁻⁷M EKC 15分钟后，最大抑制率为对照值的45±5%。这种抑制作用可被阿片类拮抗剂纳洛酮逆转，且对κ阿片类类型具有特异性。用人滋养层细胞预先孵育0.1微克/毫升胰岛激活蛋白（IAP；也称为百日咳毒素）不会改变基础腺苷酸环化酶活性，但消除了EKC对腺苷酸环化酶活性的抑制作用，表明阿片类物质对cAMP产生的影响是由IAP敏感的GTP结合蛋白介导的。此外，IAP刺激基础hPL释放；无IAP和有IAP时的对照水平分别为22.4纳克/毫升和46.5纳克/毫升。然而，预先用IAP孵育后，EKC刺激的hPL水平未改变。IAP处理细胞中cAMP和hPL反应的这种差异表明阿片受体不直接与腺苷酸环化酶偶联。这一假设通过以下实验得到证实：1）对胎盘膜的实验表明，在没有细胞质成分（仅膜）的情况下，EKC对膜腺苷酸环化酶没有影响；2）对胎盘细胞的实验表明，二丁酰-cAMP（dbcAMP）刺激hPL释放。
