Ventura C, Spurgeon H, Lakatta E G, Guarnieri C, Capogrossi M C
Laboratory of Cardiovascular Science, National Institute on Aging, National Institutes of Health, Baltimore, Md 21224.
Circ Res. 1992 Jan;70(1):66-81. doi: 10.1161/01.res.70.1.66.
We investigated the effects of mu, delta, and kappa opioid receptor stimulation on the contractile properties and cytosolic Ca2+ (Cai) of adult rat left ventricular myocytes. Cells were field-stimulated at 1 Hz in 1.5 mM bathing Ca2+ at 23 degrees C. The mu-agonist [D-Ala2,N-Me-Phe4,Gly5-ol]-enkephalin (10(-5) M) had no effect on the twitch. The delta-agonists methionine enkephalin and leucine enkephalin (10(-10) to 10(-6) M) and the kappa-agonist (trans-(dl)-3,4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl)cyclo-hexyl]- benzeneacetamide)methanesulfonate hydrate (U-50,488H; 10(-7) to 2 x 10(-5) M) had a concentration-dependent negative inotropic action. The sustained decrease in twitch amplitude due to U-50,488H was preceded by a transient increase in contraction. The effects of delta- and kappa-receptor stimulation were antagonized by naloxone and (-)-N-(3-furyl-methyl)-alpha-normetazocine methanesulfonate, respectively. In myocytes loaded with the Ca2+ probe indo-1, the effects of leucine enkephalin (10(-8) M) and U-50,488H (10(-5) M) on the twitch were associated with similar directional changes in the Cai transient. Myofilament responsiveness to Ca2+ was assessed by the relation between twitch amplitude and systolic indo-1 transient. Leucine enkephalin (10(-8) M) had no effect, whereas U-50,488H (10(-5) M) increased myofilament responsiveness to Ca2+. We subsequently tested the hypothesis that delta and kappa opioid receptor stimulation may cause sarcoplasmic reticulum Ca2+ depletion. The sarcoplasmic reticulum Ca2+ content in myocytes and in a caffeine-sensitive intracellular Ca2+ store in neurons was probed in the absence of electrical stimulation via the rapid addition of a high concentration of caffeine from a patch pipette above the cell. U-50,488H and leucine enkephalin slowly increased Cai or caused Cai oscillations and eventually abolished the caffeine-triggered Cai transient. These effects occurred in both myocytes and neuroblastoma-2a cells. In cardiac myocyte suspensions U-50,488H and leucine enkephalin both caused a rapid and sustained increase in inositol 1,4,5-trisphosphate. Thus, delta and kappa but not mu opioids have a negative inotropic action due to a decreased Cai transient. The decreased twitch amplitude due to kappa-receptor stimulation is preceded by a transient increase in contractility, and it occurs despite an enhanced myofilament responsiveness to Ca2+. The effects of delta and kappa opioids appear coupled to phosphatidylinositol turnover and, at least in part, may be due to sarcoplasmic reticulum Ca2+ depletion.(ABSTRACT TRUNCATED AT 400 WORDS)
我们研究了μ、δ和κ阿片受体激动对成年大鼠左心室肌细胞收缩特性和胞质Ca2+（Cai）的影响。细胞在23℃下于含1.5 mM 浴钙的溶液中以1 Hz进行场刺激。μ激动剂[D - Ala2，N - Me - Phe4，Gly5 - ol] - 脑啡肽（10^(-5) M）对单收缩无影响。δ激动剂甲硫氨酸脑啡肽和亮氨酸脑啡肽（10^(-10)至10^(-6) M）以及κ激动剂（反式 - （dl） - 3,4 - 二氯 - N - 甲基 - N - [2 - （1 - 吡咯烷基）环己基] - 苯乙酰胺）甲磺酸盐一水合物（U - 50,488H；10^(-7)至2×10^(-5) M）具有浓度依赖性负性肌力作用。U - 50,488H引起的单收缩幅度持续下降之前有收缩的短暂增加。δ和κ受体激动的作用分别被纳洛酮和（ - ） - N - （3 - 呋喃基 - 甲基） - α - 去甲美沙唑啉甲磺酸盐拮抗。在加载Ca^2 + 探针indo - 1的肌细胞中，亮氨酸脑啡肽（10^(-8) M）和U - 50,488H（10^(-5) M）对单收缩的影响与Cai瞬变的类似方向变化相关。通过单收缩幅度与收缩期indo - 1瞬变之间的关系评估肌丝对Ca^2 + 的反应性。亮氨酸脑啡肽（10^(-8) M）无影响，而U - 50,488H（？？？此处原文有误，推测是10^(-5) M）增加了肌丝对Ca^2 + 的反应性。我们随后检验了δ和κ阿片受体激动可能导致肌浆网Ca^2 + 耗竭的假说。在无电刺激的情况下，通过从细胞上方的膜片移液器快速添加高浓度咖啡因来探测肌细胞和神经元中对咖啡因敏感的细胞内Ca^2 + 储存中的肌浆网Ca^2 + 含量。U - 50,488H和亮氨酸脑啡肽缓慢增加Cai或引起Cai振荡，并最终消除咖啡因触发的Cai瞬变。这些作用在肌细胞和成神经细胞瘤 - 2a细胞中均发生。在心肌细胞悬液中，U - 50,488H和亮氨酸脑啡肽均引起肌醇1,4,5 - 三磷酸快速且持续增加。因此，δ和κ而非μ阿片类药物由于Cai瞬变降低而具有负性肌力作用。κ受体激动引起的单收缩幅度降低之前有收缩性的短暂增加，并且尽管肌丝对Ca^2 + 的反应性增强仍会发生。δ和κ阿片类药物的作用似乎与磷脂酰肌醇代谢相关，并且至少部分可能是由于肌浆网Ca^2 + 耗竭。（摘要截断于400字）
