Adaptive Response of Beta-Adrenergic Sensitive Adenylate Cyclase System
In the beta adrenergic adenylate cyclase system, persistent stimulation of the cells by catecholamines or analogs results in a decline of the cyclic AMP response. This phenomenon generally referred to as desensi-tization has been classified in two types by Perkins and coworkers (1). In the first one called heterologous, incubation with one agonist leads to an attenuated response to different multiple hormones operating via distinct receptors. In the second one referred to as homologous or agonist-specific, only the subsequent response to the desensitizing hormone is diminished while the efficiency of other hormones is unimpaired. This type of desensi-tization, characterized by a decrease in adenylate cyclase stimulation by beta-adrenergic agonists, is associated in most cases with a loss or disappearance of beta-adrenergic receptors (for reviews see 2,3,4): this phenomenon is called down-regulation. The down-regulated receptors can be recycled to the cell surface or destroyed within the cell (2,3,4).
KeywordsGlioma Cell Adenylate Cyclase Adrenergic Receptor Agonist Binding Adenylate Cyclase System
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