Interactions of heparin with alpha-2-adrenoceptors.
The interactions of the anticoagulant Heparin with the alpha-2-adrenoceptor in rat brain cortex membranes were investigated. Binding experiments with 3H-Clonidine were performed in both the absence and presence of Heparin. 1 uM Na-Heparin caused a significant decrease in the maximal number of binding sites (Bmax) from 129.4 fmol/mg protein to 93.7 fmol/mg protein with an associated decrease in affinity (KD = 0.79 pM vs. KD = 1.53 pM) of these binding sites. Addition of Na+-Heparin to 3H-Clonidine (3.1 nM) labelled membranes inhibited 50% of specific 3H-Clonidine binding (IC50) at a concentration of 0.95 uM. Based on our findings we conclude that the simultaneous long term administration of Na-Heparin and the antihypertensive agonist Clonidine should be regarded under consideration of the inhibitory effect of Na-Heparin to the alpha-2-adrenoceptors.
Steudle
V
V
Center of Internal Medicine, Giessen, Federal Republic of Germany.
Lübbecke
F
F
Wizemann
V
V
D000818:Animals; D001667:Binding, Competitive; D002540:Cerebral Cortex / Q000187:drug effects; D003000:Clonidine / Q000378:metabolism; D006493:Heparin / Q000494:pharmacology*; D066298:In Vitro Techniques; D051381:Rats; D011919:Rats, Inbred Strains; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects* / Q000378:metabolism
D011942:Receptors, Adrenergic, alpha; D006493:Heparin; D003000:Clonidine