Hein P, Goepel M, Cotecchia S, Michel M C
Dept of Medicine, University of Essen, Klinikum Essen, Germany.
Life Sci. 2000 Jun 23;67(5):503-8. doi: 10.1016/s0024-3205(00)00652-4.
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.
我们已经验证了这样一个假设，即与[³H]哌唑嗪相比，[³H]坦索罗辛对α1B-肾上腺素能受体的标记较少与激动剂低亲和力状态的差异识别有关。在来自大鼠肝脏以及稳定转染野生型仓鼠α1B-肾上腺素能受体或其组成型活性突变体的大鼠成纤维细胞的膜制剂中，进行了[³H]哌唑嗪和[³H]坦索罗辛的配对饱和结合实验。在所有三种情况下，[³H]坦索罗辛标记的α1B-肾上腺素能受体明显少于[³H]哌唑嗪。在去甲肾上腺素竞争结合实验中，组成型活性α1B-肾上腺素能受体的激动剂低亲和力位点的百分比最小，但[³H]坦索罗辛和[³H]哌唑嗪识别的激动剂低亲和力位点的百分比没有显著差异。我们得出结论，[³H]坦索罗辛标记的α1B-肾上腺素能受体比[³H]哌唑嗪少，但这不能完全用对激动剂低亲和力位点的标记较差来解释。
