Binding of [3H]-dihydroalprenolol and [3H]-acetobutolol to human blood platelets is not related to occupancy of beta-adrenoceptors.
Binding of [3H]-dihydroalprenolol to human platelet lysates is inhibited by (+/-)-propranolol and (+/-)-butoxamine, but less effectively by (+/-) practolol. (-)-Isoprenaline causes no significant inhibition of binding where stimulation of adenylate cyclase can be shown. Binding of [3H]-acetobutolol is also inhibited by (+/-)-propranolol. "Specific" binding of [3H]-dihydroalprenolol and [3H]-acetobutolol defined by (+/-) propranolol shows a non-classical saturation curve. 50% maximal binding is observed in the range 15-25 mM. The extent of "specific" binding is 2-fold greater for [3H]-dihydroalprenolol. Similar and rapid rates of binding of [3H]-dihydroalprenolol are observed at 4 degrees C and 20 degrees C. No stereoselectivity is observed for inhibition of [3H]-dihydroalprenolol binding by (+) and (-)-propranolol. Binding of [3H]-dihydroalprenolol and [3H]-acetobutolol may relate to the lipophilic character of these radioligands and does not represent interaction with beta-adrenoceptors.
D000070:Acebutolol / Q000378:metabolism*; D000526:Alprenolol / Q000031:analogs & derivatives*; D001792:Blood Platelets / Q000378:metabolism*; D002078:Butoxamine / Q000378:metabolism; D004082:Dihydroalprenolol / Q000378:metabolism*; D006801:Humans; D007545:Isoproterenol / Q000378:metabolism; D007700:Kinetics; D011217:Practolol / Q000378:metabolism; D011433:Propranolol / Q000378:metabolism; D011941:Receptors, Adrenergic / Q000032:analysis*; D011943:Receptors, Adrenergic, beta / Q000032:analysis*
D011941:Receptors, Adrenergic; D011943:Receptors, Adrenergic, beta; D002078:Butoxamine; D004082:Dihydroalprenolol; D000070:Acebutolol; D000526:Alprenolol; D011433:Propranolol; D007545:Isoproterenol; D011217:Practolol