Yu X C, Li H Y, Wang H X, Wong T M
Department of Physiology and Institute of Cardiovascular Science and Medicine, Faculty of Medicine, The University of Hong Kong, Hong Kong.
J Mol Cell Cardiol. 1998 Feb;30(2):405-13. doi: 10.1006/jmcc.1997.0604.
In order to determine the effect of kappa-opioid receptor agonist on the beta1-adrenoceptor stimulation in the heart, the effects of norepinephrine (NE), a beta1-adrenoceptor agonist, on contraction and electrically induced intracellular calcium ([Ca2+]i) transient in the single rat ventricular myocyte pretreated with a kappa-opioid receptor agonist, trans-(+/-)-3, 4-dichloro-N-methyl-N-(2-[1-pyrrolidinyl]cyclohexyl)-benzeneacetamide (U50,488H), at 0.01-1 microM were studied with a video edge tracker method and a spectrofluorometric method using fura-2 as calcium indicator, respectively. NE at 0.01-10 microM augmented both twitch amplitude and electrically induced [Ca2+]i transient dose-dependently, which were abolished by propranolol at 1 microM, a beta-adrenoceptor antagonist. The effects of NE on both contraction and [Ca2+]i transient were attenuated in a dose-dependent manner by U50,488H at 0.01-1 microM, which itself had no effect at all. The maximum response ( Emax) was decreased, while the concentration that produces 50% of the maximum response (EC50) was enhanced, by U50, 488H. The inhibitory effects of U50,488H on beta-adrenoceptor stimulation were completely blocked by pretreatment with norbinaltorphimine, a specific kappa-opioid receptor antagonist at 1 microM, or preincubation with pertussis toxin (PTX) at 200 ng/ml for 6 h. On the other hand, the inhibition on NE-induced augmentation in electrically induced [Ca2+]i transient by U50,488H was not affected by pretreatment with U73122, a specific inhibitor of phospholipase C (PLC), at 10 microM for 30 min. U50,488H attenuated the augmentation of the electrically stimulated [Ca2+]i transient induced by forskolin at 0.1 and 0.5 microM. It did not, however, affect the augmentation of the electrically induced [Ca2+]i transient by N6, 2'-O-dibutyryl adenosine cyclic monophosphate (DB-cAMP). The results suggest that kappa-opioid receptor stimulation by U50,488H at 10(-6 )M or lower may inhibit the effects of beta-adrenoceptor stimulation by acting at a PTX-sensitive G-protein and AC, but not via the phosphoinositol pathway.
为了确定κ-阿片受体激动剂对心脏中β1-肾上腺素能受体刺激的影响，使用视频边缘跟踪法和以fura-2作为钙指示剂的荧光分光光度法，研究了β1-肾上腺素能受体激动剂去甲肾上腺素（NE）对预先用κ-阿片受体激动剂反式-(+/-)-3,4-二氯-N-甲基-N-(2-[1-吡咯烷基]环己基)-苯乙酰胺（U50,488H）在0.01 - 1μM预处理的单个大鼠心室肌细胞收缩和电诱导的细胞内钙（[Ca2+]i）瞬变的影响。0.01 - 10μM的NE剂量依赖性地增加了收缩幅度和电诱导的[Ca2+]i瞬变，1μM的β-肾上腺素能受体拮抗剂普萘洛尔可消除这些作用。0.01 - 1μM的U50,488H以剂量依赖性方式减弱了NE对收缩和[Ca2+]i瞬变的影响，而其本身没有任何作用。U50,488H使最大反应（Emax）降低，同时产生最大反应50%的浓度（EC50）增加。U50,488H对β-肾上腺素能受体刺激的抑制作用被1μM的特异性κ-阿片受体拮抗剂去甲纳曲酮预处理或200 ng/ml百日咳毒素（PTX）预孵育6小时完全阻断。另一方面，10μM的磷脂酶C（PLC）特异性抑制剂U73122预处理30分钟对U50,488H抑制NE诱导的电诱导[Ca2+]i瞬变增加没有影响。U50,488H减弱了0.1和0.5μM福斯可林诱导的电刺激[Ca2+]i瞬变的增加。然而，它不影响N6,2'-O-二丁酰腺苷环磷酸（DB-cAMP）诱导的电诱导[Ca2+]i瞬变的增加。结果表明，10(-6)M或更低浓度的U50,488H刺激κ-阿片受体可能通过作用于对PTX敏感的G蛋白和腺苷酸环化酶（AC）来抑制β-肾上腺素能受体刺激的作用，但不是通过磷酸肌醇途径。
