Molecular cloning and functional studies of alpha_1 adrenoceptors

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alpha_1 Adrenoceptor plays important physiological roles in blood pressure, lipid metabolism, urinary tissues and central nervous system. In the present research project. we carried out molecular biological and classical pharmacological studies in order to clarify alpha_1 adrenoceptor functions.1 . Molecular cloning of rabbit alpha_1 adrenoceptor subtypes : We screened rabbit liver cDNA library and identified alpha_<1a> alpha_<1b> and alpha_<1d> subtypes. Rabbit alpha_<1b> and alpha_<1d> subtypes showed high homology and the same pharmacological characters to those of other species reported previously. However, three splice variants were identified in rabbit alpha_<1b> adrenoceptor, which had uniqe sequence in C-terminal and showed different tissue distribution in rabbit.2. Identification of native alpha_1 adrenoceptor subtypes : Native alpha_1 adrenoceptors were examined in radioligand binding and functional experiments and identified in the following tissues ; alpha_<1A> and alpha_<1L> in human prostate, alpha_<1L> in human urethra, alpha_<1B> in human aorta, alpha_<1A> and alpha_<1L> in rat prostate and rabbit iris.3. Functional analysis of alpha_1 adrenoceptors with cytosensor : Human alpha_<1a> alpha_<1b> and alpha_<1d> adrenoceptors were stably expressed in CHO cells and the extracellular acidification rate (EAR) was measured with cytosensor. EAR increased concentration-dependently in response to alpha agonists such as noradrenaline and clonidine. Detailed analyses of concentration-response urves revealed full agonist, partial agonist, spare receptor and propriety of Schild plot, showing that classical receptor theory is applicable to this system.