Binding of anandamide to bovine serum albumin.
The endocannabinoid anandamide is of lipid nature and may thus bind to albumin in the vascular system, as do fatty acids. The knowledge of the free water-phase concentration of anandamide is essential for the investigations of its transfer from the binding protein to cellular membranes, because a water-phase shuttle of monomers mediates such transfers. We have used our method based upon the use of albumin-filled red cell ghosts as a dispersed biological "reference binder" to measure the water-phase concentrations of anandamide. These concentrations were measured in buffer (pH 7.3) in equilibrium with anandamide bound to BSA inside resealed human red cell membranes at low molar ratios below one. Data were obtained at 0 degrees C, 10 degrees C, 23 degrees C, and 37 degrees C. The equilibrium dissociation constant (Kd) increases with temperature from 6.87 +/- 0.53 nM at 0 degrees C to 54.92 +/- 1.91 nM at 37 degrees C. Regression analyses of the data suggest that BSA has one high-affinity binding site for anandamide at all four temperatures. The free energy of anandamide binding (DeltaG0) is calculated to -43.05 kJ mol-1 with a large enthalpy (DeltaH0) contribution of -42.09 kJ mol-1. Anandamide has vasodilator activity, and the binding to albumin may mediate its transport in aqueous compartments.
Bojesen
Inge N
IN
Department of Medical Biochemistry and Genetics, Lab. B., University of Copenhagen, The Panum Institute, Blegdamsvej 3, DK-2200 Copenhagen N, Denmark. norby@imbg.ku.dk
Hansen
Harald S
HS
D000818:Animals; D001095:Arachidonic Acids / Q000378:metabolism*; D001665:Binding Sites; D002417:Cattle; D063388:Endocannabinoids; D007700:Kinetics; D053284:Polyunsaturated Alkamides; D011485:Protein Binding; D012044:Regression Analysis; D012710:Serum Albumin, Bovine / Q000378:metabolism*; D013696:Temperature
D001095:Arachidonic Acids; D063388:Endocannabinoids; D053284:Polyunsaturated Alkamides; D012710:Serum Albumin, Bovine; C078814:anandamide