Effect of serum, alpha-1 acid glycoprotein, lipoproteins and albumin on human mononuclear leucocyte beta-adrenoceptors.
The effects of serum, alpha-1 acid glycoprotein (AAG), serum lipoproteins (SLP) and human serum albumin (HSA) on 3H-(-)-dihydroalprenolol (3H-(-)-DHA) binding and (-)-isoproterenol ((-)-IPR) induced cyclic AMP (cAMP) elevation in human peripheral blood mononuclear leucocytes (MNL) were investigated. The saturable binding of 3H-(-)-DHA was decomposed into two classes of binding sites with maximum binding capacity of approximately 1400 and 30000 sites/cell and with dissociation constants (Kd) of approximately 0.7 and 65 nM. Stimulation of the MNL beta-adrenoceptors by (-)-IPR caused a concentration dependent cAMP accumulation (EC50 approximately 0.2 microM) with maximum level approximately 250% above basal. For all single leucocyte preparations, 30-35 min. exposure to serum, AAG and SLP increased the number of beta-adrenoceptors with 100-200% and the maximal responsiveness to (-)-IPR with 30-90%. The presence of proteins did not change the Kd or the EC50. (-)-Alprenolol inhibited concentration dependently the serum induced increment in (-)-IPR-responsiveness. Serum, AAG and SLP did also increase the number of low affinity binding sites with 25-40% without effect on the Kd. HSA had no consistent effect on beta-adrenergic binding or stimulation. The present study shows that serum, AAG and SLP influence the number and function of MNL beta-adrenoceptors in vitro.
D000526:Alprenolol / Q000378:metabolism; D001769:Blood; D001798:Blood Proteins / Q000494:pharmacology*; D000242:Cyclic AMP / Q000096:biosynthesis; D004082:Dihydroalprenolol / Q000378:metabolism; D006801:Humans; D007545:Isoproterenol / Q000378:metabolism; D007962:Leukocytes / Q000187:drug effects* / Q000378:metabolism; D008074:Lipoproteins / Q000494:pharmacology; D009961:Orosomucoid / Q000494:pharmacology; D011433:Propranolol / Q000378:metabolism; D011943:Receptors, Adrenergic, beta / Q000187:drug effects* / Q000378:metabolism; D012709:Serum Albumin / Q000494:pharmacology; D013806:Theophylline / Q000378:metabolism
D001798:Blood Proteins; D008074:Lipoproteins; D009961:Orosomucoid; D011943:Receptors, Adrenergic, beta; D012709:Serum Albumin; D004082:Dihydroalprenolol; D000526:Alprenolol; D011433:Propranolol; D013806:Theophylline; D000242:Cyclic AMP; D007545:Isoproterenol