Zimányi I, Pessah I N
Department of Veterinary Pharmacology and Toxicology, University of California, Davis 95616.
J Pharmacol Exp Ther. 1991 Mar;256(3):938-46.
Sarcoplasmic reticulum (SR) vesicles prepared from rat ventricle muscle are isolated, and their [3H]ryanodine-binding and calcium transport properties are studied in detail under active loading conditions in the presence of pyrophosphate. Experiments are performed in tandem with rabbit skeletal SR under identical conditions to allow direct comparisons of the mechanisms by which activators and inhibitors influence the calcium release channel. Ca(++)-induced Ca++ release is demonstrated with both preparations and the cardiac channel is about 1.5-fold more sensitive to activation by Ca++, which is in excellent quantitative agreement with the ability of Ca++ to activate [3H]ryanodine-binding sites. The cardiac and skeletal receptors show major quantitative differences with respect to sensitivity to pharmacologic modulators, cations and pH. The inhibitors ruthenium red, Mg++ and neomycin are significantly more potent in inhibiting the skeletal receptor, whereas the activators daunorubicin and caffeine are significantly more potent towards the cardiac receptor. The ATP analog, beta,gamma-methyleneadenosine 5'-triphosphate, enhances the binding of [3H]ryanodine to the high-affinity site in skeletal SR by a factor of 4 but has a negligible effect on the cardiac receptor, although at suboptimal Ca++ for the binding of ryanodine, beta,gamma-methyleneadenosine 5'-triphosphate activates the cardiac receptor to a greater extent. High levels of salt (1 M NaCl) enhance the rate of [3H]ryanodine association with its binding sites in both preparations, although they selectively reduce the binding-site capacity in skeletal SR due to a failure to maintain a stable equilibrium. Although high- and low-affinity binding of [3H]ryanodine have a similar response to changing pH, the skeletal receptors are significantly more sensitive to pH.(ABSTRACT TRUNCATED AT 250 WORDS)
从大鼠心室肌制备的肌浆网（SR）囊泡被分离出来，并在焦磷酸存在的主动加载条件下，详细研究其[3H]雷诺丁结合和钙转运特性。在相同条件下与兔骨骼肌SR同时进行实验，以便直接比较激活剂和抑制剂影响钙释放通道的机制。两种制剂均证明了Ca(++)诱导的Ca++释放，并且心脏通道对Ca++激活的敏感性约高1.5倍，这与Ca++激活[3H]雷诺丁结合位点的能力在定量上非常吻合。心脏和骨骼肌受体在对药理调节剂、阳离子和pH的敏感性方面存在主要的定量差异。抑制剂钌红、Mg++和新霉素在抑制骨骼肌受体方面明显更有效，而激活剂柔红霉素和咖啡因对心脏受体的作用明显更强。ATP类似物β,γ-亚甲基腺苷5'-三磷酸使[3H]雷诺丁与骨骼肌SR中高亲和力位点的结合增加4倍，但对心脏受体的影响可忽略不计，尽管在雷诺丁结合的次优Ca++条件下，β,γ-亚甲基腺苷5'-三磷酸在更大程度上激活心脏受体。高浓度盐（1 M NaCl）提高了两种制剂中[3H]雷诺丁与其结合位点的结合速率，尽管由于未能维持稳定平衡，它们选择性地降低了骨骼肌SR中的结合位点容量。尽管[3H]雷诺丁的高亲和力和低亲和力结合对pH变化有类似反应，但骨骼肌受体对pH更敏感。（摘要截断于250字）
