Article: article from journal or magazin.
Comparison of [3H]tamsulosin and [3H]prazosin binding to wild-type and constitutively active alpha1B-adrenoceptors.
We have tested the hypothesis that smaller alpha1B-adrenoceptor labeling by [3H]tamsulosin compared to [3H]prazosin is related to differential recognition of agonist low affinity states. Paired saturation binding experiments with [3H]prazosin and [3H]tamsulosin were performed in membrane preparations from rat liver and Rat- fibroblasts stably transfected with wild-type hamster alpha1B-adrenoceptors or a constitutively active mutant thereof. In all three settings [3H]tamsulosin labeled significantly fewer alpha1B-adrenoceptors than [3H]prazosin. In noradrenaline competition binding experiments, the percentage of agonist low affinity sites was smallest for the constitutively active alpha1B-adrenoceptor but the percentage of agonist low affinity sites recognized by [3H]tamsulosin and [3H]prazosin did not differ significantly. We conclude that [3H]tamsulosin labels fewer alpha1B-adrenoceptors than [3H]prazosin but this is not fully explained by a poorer labeling of agonist low affinity sites.
Adrenergic alpha-Antagonists/metabolism, Animals, Cricetinae, Male, Prazosin/metabolism, Radioligand Assay, Rats, Rats, Wistar, Receptors, Adrenergic, alpha-1/metabolism, Sulfonamides/metabolism, Tritium
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