The detection of β-adrenoceptors on murine lymphocytes

Abstract

The β-adrenoceptor antagonist ( 125I)-iodohydroxybenzyl pindolol was used to detect and characterise β-adrenoceptors on the surface of mouse lymphocytes by a direct radioligand receptor assay using intact viable cells. The binding was stereoselective and appeared to be with a β 2-type receptor as shown by competition with a number of adrenergic reagents. Scatchard analysis of the ligand binding demonstrated approximately 3000 binding sites per cell with an average dissociation constant ( K d ) of 0.92 nM. Little variation in binding characteristics was observed between lymphocytes from individual mice of either sex or in 24 different inbred mouse strains. In addition no significant differences were noted between T and B enriched lymphocyte populations, i.e. there was no functional polymorphism of the β-adrenoceptor on mouse lymphocytes. Thymocytes carried a lower affinity receptor which may be related to their functional immaturity. By using antisera specific for murine cell surface alloantigens, the β-adrenoceptor was shown not to be associated with the H-2K, H-2D, Ia, Ly−1, −2, −3, −4, or −5, Tla or Thy antigens. However, specific antisera for the Ly-7 antigen did partially inhibit IHYP binding. The results show that lymphocytes have a β 2-adrenoceptor which closely resembles the receptor on other tissues.