Galant S P, Allred S
J Lab Clin Med. 1981 Aug;98(2):227-37.
Beta adrenergic receptors have been previously characterized in human neutrophil sonicates. In the present study the intact neutrophil has been assessed for the number and affinity of beta adrenergic binding sites by using the antagonist DNA. Agonist and antagonist potencies, characterized by their effect on DHA binding and cyclic AMP accumulation, are compared with agonist inhibition of lysosomal enzyme (beta glucuronidase) release. Criteria for beta adrenergic receptor identification were successfully demonstrated. At 30 degrees C, beta adrenergic binding was rapid (t 1/2 2 min) and reversible (t 1/2 9 min). Receptor binding was saturable, revealing approximately 900 high-affinity receptors per neutrophil with DHA concentrations of 0.1 to 10 nM. By utilizing both equilibrium and kinetic techniques, the KD was determined to be approximately 0.6 nM. Agonists and antagonists competed for DHA binding in a manner consistent with their effect on cyclic AMP generation. Rank order potency was suggestive of a beta-2 receptor: isoproterenol greater than epinephrine greater than norepinephrine. Stereoselectivity was shown by the greater potency of L-propranolol compared to the D isomer. A high degree of receptor-adenylate cyclase coupling efficiency was suggested by the observation that with only 1% receptor occupancy isoproterenol stimulated 50% maximal cyclic AMP generation. Finally, there was an excellent correlation between the isoproterenol concentration which resulted in 50% of maximal inhibition of beta glucuronidase release (Ki) and that causing 50% maximal cyclic AMP stimulation (Kact), suggestive of a close relationship between beta adrenergic-induced adenylate cyclase activation and beta adrenergic regulation of neutrophil lysosomal enzyme release. The data presented suggest that the use of the intact neutrophil for study of the beta adrenergic receptor is feasible and may provide information which is considerably more closely related to modulation of physiological function by neurohormones than is possible with disrupted cell preparations.
β肾上腺素能受体先前已在人中性粒细胞超声裂解物中得到表征。在本研究中，通过使用拮抗剂二氢麦角胺（DHA）评估了完整中性粒细胞上β肾上腺素能结合位点的数量和亲和力。将以其对DHA结合和环磷酸腺苷（cAMP）积累的影响为特征的激动剂和拮抗剂效力，与激动剂对溶酶体酶（β-葡萄糖醛酸酶）释放的抑制作用进行比较。成功证明了β肾上腺素能受体鉴定的标准。在30℃时，β肾上腺素能结合迅速（半衰期2分钟）且可逆（半衰期9分钟）。受体结合具有饱和性，在DHA浓度为0.1至10 nM时，每个中性粒细胞显示约900个高亲和力受体。通过使用平衡和动力学技术，确定解离常数（KD）约为0.6 nM。激动剂和拮抗剂以与其对cAMP生成的影响一致的方式竞争DHA结合。效价顺序提示为β2受体：异丙肾上腺素＞肾上腺素＞去甲肾上腺素。左旋普萘洛尔比右旋异构体效力更强，显示出立体选择性。观察到仅1%的受体占有率时异丙肾上腺素就能刺激50%的最大cAMP生成，提示受体-腺苷酸环化酶偶联效率很高。最后，导致β-葡萄糖醛酸酶释放50%最大抑制的异丙肾上腺素浓度（Ki）与引起50%最大cAMP刺激的浓度（Kact）之间存在极好的相关性，这表明β肾上腺素能诱导的腺苷酸环化酶激活与中性粒细胞溶酶体酶释放的β肾上腺素能调节之间存在密切关系。所呈现的数据表明，使用完整中性粒细胞研究β肾上腺素能受体是可行的，并且可能提供比使用破碎细胞制剂更能与神经激素对生理功能的调节密切相关的信息。
