Dillon J S, Gu X H, Nayler W G
Department of Medicine, University of Melbourne, Austin Hospital, Heidelberg, Victoria, Australia.
J Mol Cell Cardiol. 1988 Aug;20(8):725-35. doi: 10.1016/s0022-2828(88)80017-8.
The [3H]-prazosin binding activity of membranes isolated from aerobically perfused, ischaemic and reperfused cat and rat hearts was investigated. Alpha 1 adrenoceptors in membranes from aerobically perfused cat hearts had a KD of 0.363 +/- 0.067 nM and a Bmax of 68.8 +/- 7.0 fmol/mg protein; 30 min normothermic global ischaemia caused an increase (P less than 0.01) in density (Bmax, 111.4 +/- 9.3 fmol/mg protein), without any change in affinity (KD 0.430 +/- 0.069 nM). Post-ischaemic reperfusion (15 min) caused the Bmax to return to control values, with no change in KD. Membranes isolated from aerobically perfused rat hearts contained a single population of high affinity alpha 1 adrenoceptor binding sites, with a KD of 0.092 +/- 0.02 nM and a Bmax of 43.02 +/- 2.49 fmol/mg protein. Neither global nor low-flow (0.1 ml/min) ischaemia for either 30 or 60 min, nor post-ischaemic reperfusion, caused any change in either the affinity or density of these binding sites. In both species, and under all the above experimental conditions, the selectivity of the alpha 1 adrenoceptor binding sites was maintained, with phentolamine much greater than rauwolscine in displacing bound [3H]-prazosin. These results show that the ability of ischaemia to increase alpha 1 adrenoceptor density in cardiac membranes is species specific, and that it can occur as a direct (as opposed to a reflex) response to ischaemia.
研究了从需氧灌注、缺血及再灌注的猫和大鼠心脏中分离出的膜的[3H]-哌唑嗪结合活性。需氧灌注的猫心脏膜中的α1肾上腺素能受体的解离常数（KD）为0.363±0.067 nM，最大结合容量（Bmax）为68.8±7.0 fmol/mg蛋白质；30分钟常温全心缺血导致密度增加（P<0.01）（Bmax为111.4±9.3 fmol/mg蛋白质），而亲和力无任何变化（KD为0.430±0.069 nM）。缺血后再灌注（15分钟）使Bmax恢复到对照值，KD无变化。从需氧灌注的大鼠心脏中分离出的膜含有单一群体的高亲和力α1肾上腺素能受体结合位点，KD为0.092±0.02 nM，Bmax为43.02±2.49 fmol/mg蛋白质。30或60分钟的全心或低流量（0.1 ml/分钟）缺血以及缺血后再灌注均未导致这些结合位点的亲和力或密度发生任何变化。在这两个物种中，以及在上述所有实验条件下，α1肾上腺素能受体结合位点的选择性得以维持，酚妥拉明在取代结合的[3H]-哌唑嗪方面远大于萝芙木碱。这些结果表明，缺血增加心脏膜中α1肾上腺素能受体密度的能力具有物种特异性，并且它可以作为对缺血的直接（而非反射性）反应而发生。
