MOLECULAR DISTRIBUTION OF HUMAN ADRENERGIC RECEPTORS

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The long term objective of this project is to relate adrenergic receptor (AR) subtype molecular distribution to hormone/drug interaction and evoked human physiologic responses in health and disease. Within this context, the overall focus of this grant is characterization of the molecular distribution of human AR subtypes. ARs play key roles in the regulation of physiologic processes such as myocardial blood flow, smooth muscle contraction, liver metabolism, and control of systemic arterial blood pressure, and have been shown to be altered in number and function in various disease states. Recently the principal investigator has discovered striking species heterogeneity in the distribution of AR subtypes, making characterization and distribution of AR subtypes in human tissue essential. Therefore we propose characterizing the distribution of all nine cloned AR subtypes in human tissue in order to test the hypothesis that AR subtype specific changes occur during diseases of the cardiovascular system. Selective agonists and antagonists have not yet been developed for each AR subtype, hence direct techniques such as autoradiography and ligand binding cannot be used for this project. The principal investigator is unique in having human sequence for all nine AR subtype genes and access to human tissues, enabling in situ hybridization techniques to be employed in localizing the distribution of mRNA encoding AR subtypes to specific cell layers in human tissue sections. Therefore the first major aim is evaluation of the distribution of AR subtype mRNA in normal tissue from the cardiovascular system, peripheral tissues, and central nervous system will be used for an extensive survey of human AR localization; preliminary studies using tissue sections from human renal artery, hippocampus, [prostate, and spinal cord] demonstrate the viability of RNA in tissue obtained at rapid autopsy. The second major aim of this proposal is evaluation of changes in distribution of AR subtypes in human cardiovascular disease. Selected human tissue from numerous patients with and without coincident cardiovascular diseases is available to the principal investigator for discarded surgical specimens. Surgical specimens will be used to quantitate AR subtype mRNA changes (compared with normal tissue) in patients with selected coincident diseases (see specific aims for a concise list of selected diseases and tissues proposed for this study). Many drugs used in modulating cardiovascular responses are agonists and antagonists of ARs; therefore defining the location of various AR subtypes in human tissues enhances the development of more selective pharmacological agents designed for specific physiological responses. In addition, quantitation of changes in mRNA encoding distinct AR subtypes in specific tissues for a given disease (combined with future direct studies of receptor protein once selective ligands and antibodies are available), is critical for ultimately understanding mechanisms of human diseases involving the adrenergic nervous system.