Non-homogeneous distribution of beta 1- and beta 2-adrenoceptors in various human tissues.
The distribution of beta 1- and beta 2-adrenoceptor subtypes was determined in membranes obtained from the right atrium, abdominal fat pad, kidney, lung and liver of each of three human subjects. The number of each beta-adrenoceptor subtype was calculated by nonlinear least-squares computer analysis of the competition curve of (-) [125I]iodocyanopindolol (125I-CYP) binding, using beta 1-selective antagonist CGP 20712A and beta 2-selective antagonist ICI 118,551. Competition studies using CGP 20712A indicated that both beta 1- and beta 2-adrenoceptor subtypes coexist in all five tissues, with marked difference in the relative proportion of beta 1- and beta 2-adrenoceptors among these tissues. Most notably, the existence of beta 1-subtypes could be clearly shown in the lung (27%) and liver (18%); according to previous reports, beta 2-subtypes are found almost exclusively in the lung and liver in humans. Regarding the kidney, the present results (beta 2-subtypes: 68%) also differed from previous human data in that beta 1-subtypes predominated. Consistent results were obtained in experiments with ICI 118,551. These results provide a new insight into the mechanisms by which catecholamines regulate a particular beta-adrenergic function in these tissues.
Department of Hospital Pharmacy, Tenri Hospital, Nara, Japan.
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M
Sano
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T
Yoshimasa
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T
Yagura
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I
Yamamoto
D000273:Adipose Tissue / Q000378:metabolism; D001667:Binding, Competitive; D002462:Cell Membrane / Q000378:metabolism; D006801:Humans; D007457:Iodine Radioisotopes; D020120:Iodocyanopindolol; D007668:Kidney / Q000378:metabolism; D007700:Kinetics; D008099:Liver / Q000378:metabolism; D008168:Lung / Q000378:metabolism; D009206:Myocardium / Q000378:metabolism; D009928:Organ Specificity; D010869:Pindolol / Q000031:analogs & derivatives* / Q000378:metabolism; D011869:Radioligand Assay; D011943:Receptors, Adrenergic, beta / Q000032:analysis / Q000145:classification* / Q000378:metabolism
D007457:Iodine Radioisotopes; D011943:Receptors, Adrenergic, beta; D020120:Iodocyanopindolol; D010869:Pindolol