title: The characteristics of low and high affinity [3H]-prazosin binding to membranes from rat renal cortex.
abstract: The characteristics of [3H]-prazosin binding in renal cortical membranes of the rat have been assessed under a variety of buffer conditions. At 37 degrees, in Krebs' phosphate and Tris buffer, [3H]-prazosin bound to two sites, a small population of high affinity sites with properties of alpha1-adrenoceptors and a much larger population of low affinity sites with different characteristics. High affinity [3H]-prazosin binding was insensitive to Na+, K+, Ca2+ and Mg2+ ions, but low affinity [3H]-prazosin binding was markedly increased in Krebs' phosphate or sodium phosphate buffer and further enhanced in membranes pretreated with EGTA. Binding was decreased in the presence of Ca2+, the decrease in binding mainly being due to a decrease in the number of low affinity sites labelled by the ligand. Low affinity [3H]-prazosin binding was increased at 37 degrees and relatively insensitive to alpha-adrenoceptor antagonists which were weak competitors while catecholamines failed to compete for low affinity binding. Scatchard plots of [3H]-prazosin binding performed using (-)-noradrenaline (1 mM) to define non-specific binding defined binding only to alpha 1-adrenoceptors. This provides a means of differentiating high and low affinity [3H]-prazosin binding.
mesh_terms: D000818:Animals; D001665:Binding Sites / Q000187:drug effects; D001667:Binding, Competitive; D002118:Calcium / Q000494:pharmacology; D002412:Cations / Q000494:pharmacology; D002462:Cell Membrane / Q000378:metabolism; D007672:Kidney Cortex / Q000378:metabolism*; D011224:Prazosin / Q000378:metabolism*; D051381:Rats; D011942:Receptors, Adrenergic, alpha / Q000378:metabolism*
chemical_list: D002412:Cations; D011942:Receptors, Adrenergic, alpha; D002118:Calcium; D011224:Prazosin