Beta adrenergic receptors and cyclic AMP levels in intact human lymphocytes: Effects of age and gender |
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Authors: | James P. Halper J.John Mann Marc E. Weksler John P. Bilezikian John A. Sweeney Richard P. Brown Trevor Golbourne |
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Affiliation: | Department of Psychiatry, Cornell University Medical College Payne Whitney Psychiatric Clinic, 525 East 68th Street New York, New York 10021, USA |
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Abstract: | A saturable, stereospecific high affinity beta2 adrenergic receptor was demonstrated on intact human peripheral blood lymphocytes using the ligand [125I]-iodocyanopindolol ([125I]ICYP). A method is described for parallel measurements of saturation binding isotherms and isoproterenol-cAMP responsiveness in split samples of intact lymphocytes isolated from 40 ml. of whole blood. A significant positive correlation between beta receptor density (Bmax) and the ratio of maximal isoproterenol-generated cAMP to basal levels was found in healthy subjects (r=0.65, p < 0.001). A significant positive correlation was found between age and the fold increase over basal cAMP levels induced by isoproterenol. Older females had a significantly higher fold increase in cAMP levels after isoproterenol than older males. These effects were largely accounted for by the lower basal levels of cAMP in older subjects. Beta receptor binding indices (Bmax and KD) did not differ between males and females, or change with aging. The effects of age and sex upon cAMP levels appear to be at least partly mediated by mechanisms independent of the beta receptor. The method, which describes a convenient assay for parallel measurement of beta receptor binding and cAMP levels in small blood samples, represents a useful model for studying human beta receptor function. |
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