DISTRIBUTION OF BETA(1)-ADRENOCEPTOR AND BETA(2)-ADRENOCEPTOR SUBTYPES IN VARIOUS MOUSE-TISSUES

The distribution of beta1- and beta2-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 [I-125]-(-)iodocy anopindolol gave linear plots and the order of the density of total be ta-adrenoceptors was lung > submandibular gland > spleen > kidney > he art. Competition binding studies using beta1-selective antagonist CGP2 0712A indicated that all tissues examined possessed both high and low affinity sites which approximately stand for beta1- and beta2-adrenoce ptor subtypes respectively despite the notable difference in the ratio s of high and low affinity sites depending on the tissues. The order o f the occupancy of high affinity sites was submandibular gland (71%), heart (55%), spleen (18%), kidney (17%), lung (14%). These results wil l be helpful to elucidate the regulatory mechanism which underlies bet a-adrenergic functions in mice.