大鼠心室β2肾上腺素受体的分布及功能

DISTRIBUTION AND INOTROPIC RESPONSE OF β2-ADRENOCEPTOR IN RAT VENTRICLE

利用放射配基结合实验及离体大鼠乳头肌灌流实验方法分析β２肾上腺素受体（β２～ＡＲ）在心室中的分布及其介导的正性变力效应。β２选择性拮抗剂ＩＣＩ１１８，５５１与受体结合包含高、低亲和性两个位点，Ｋ１值分别与β２－和β１－ＡＲ的亲和性相符，各占４３％与５７％。ＩＣＩ１１８，５５１与ＣＧＰ２０７１２Ａ均可使异丙基肾上腺素（ＩＳＯ）的浓度－效应曲线显著右移，ｐＫＢ值分别为７．３６与８．５４，均介于它们与β１－和β２－ＡＲ的亲和性之间。以上结果表明：大鼠心室中共存β１－与β２－ＡＲ两种亚型，约各占一半；β１与β２－ＡＲ均介导ＩＳＯ引起的正性变力效应。

he distribution and inotropic effect of β2-AR in rat ventricules were studied by method of radioligand binding assays and contractile response measurement in isolated papillary muscles.The results showed that ICI 118,551 competitively inhibited 125I-Pindolol binding with 43%high(pkr=8.O±O.16)and 57% low (pkI=5.7 ±0.15)affinity sites.The K1values of both sites were coincident with KD value for β2-and β1-AR,respectively.Concentra- tion-response curves for ispro terenol were significently shifted to the right by ICI 118,551 and CGP 20712A.Their pKB values were between the KD values for β2-and β2-AR.The data suggest that β2-and β-AR coexist in rat ventricle and β2-AR also mediated positive inotropic response.