Distribution of beta 1- and beta 2-adrenoceptor subtypes in various mouse tissues

The distribution of beta 1- and beta 2-adrenoceptor subtypes in mice was determined in crude membranes prepared from the submandibular gland, lung, spleen, heart and kidney, all of which are major target tissues of sympathoadrenal neurons. Scatchard analysis using [125I]-(-)iodocyanopindolol gave linear plots and the order of the density of total beta-adrenoceptors was lung > submandibular gland > spleen > kidney > heart. Competition binding studies using beta 1-selective antagonist CGP20712A indicated that all tissues examined possessed both high and low affinity sites which approximately stand for beta 1- and beta 2-adrenoceptor subtypes respectively despite the notable difference in the ratios of high and low affinity sites depending on the tissues. The order of the occupancy of high affinity sites was submandibular gland (71%), heart (55%), spleen (18%), kidney (17%), lung (14%). These results will be helpful to elucidate the regulatory mechanism which underlies beta-adrenergic functions in mice.