Paskvalin M, Khatter J C
Department of Medicine, University of Manitoba, Winnipeg, Canada.
Life Sci. 1997;61(14):1361-9. doi: 10.1016/s0024-3205(97)00681-4.
Possible species differences and organ specificity in contractile or relaxation effects of an endogenous inotropic factor (EIF) isolated and purified from porcine heart left ventricle were examined in guinea pig and rat isolated atria, trabeculae and aortic smooth muscle rings. EIF demonstrated a dose-dependent increase in contractile force in guinea pig and rat atria and right ventricle trabeculae. The magnitude of the contractile effect was significantly lower in both the preparations of rat species as compared with guinea pig. In rat isolated aortic rings, EIF had no effect on the basal muscle tone. However, when rings were pre-contracted with phenylephrine EIF caused dose-dependent relaxation of the muscle. When aortic rings isolated from guinea pig were used, EIF induced a dose-dependent contraction which could be blocked by pre-treating the rings with either 2 microM phentolamine or 20 microM prazosin. When these same pre-treated rings were pre-contracted with histamine before the addition of EIF, a dose-dependent relaxation of guinea pig aortic smooth muscle rings was observed. Also depletion of catecholamines from the pre-synaptic nerve terminals innervating the aortic rings, using either 0.6 mM rauwolscine or reserpinizing (5 mg/Kg) the guinea pig 24 hours before sacrificing the animal, completely prevented EIF-induced contraction of the aortic rings. Instead EIF caused a dose dependent relaxation of the histamine pre-contracted aortic rings similar to that observed in rat aortic rings. The relaxation effect of EIF was demonstrated to be endothelium dependent and nitric oxide mediated in both species since EIF-induced relaxation could be inhibited by 2 microM L-NAME, a nitric oxide synthase inhibitor. Atropine (0.2 microM) or Indomethacin (10 microM) had no significant effect on EIF-induced relaxation of either guinea pig or rat aortic smooth muscle.
从猪心脏左心室分离纯化得到的内源性肌力因子（EIF）对豚鼠和大鼠离体心房、小梁及主动脉平滑肌环的收缩或舒张作用的潜在种属差异和器官特异性进行了研究。EIF使豚鼠和大鼠心房及右心室小梁的收缩力呈剂量依赖性增加。与豚鼠相比，大鼠两种制剂中的收缩效应幅度均显著较低。在大鼠离体主动脉环中，EIF对基础肌张力无影响。然而，当环用去氧肾上腺素预收缩时，EIF可引起肌肉剂量依赖性舒张。当使用从豚鼠分离的主动脉环时，EIF诱导剂量依赖性收缩，该收缩可通过用2微摩尔酚妥拉明或20微摩尔哌唑嗪预处理环来阻断。当在添加EIF之前用组胺预收缩这些相同的预处理环时，观察到豚鼠主动脉平滑肌环的剂量依赖性舒张。同样，在处死动物前24小时，使用0.6毫摩尔劳丹素或使豚鼠利血平化（5毫克/千克）来耗尽支配主动脉环的突触前神经末梢中的儿茶酚胺，可完全阻止EIF诱导的主动脉环收缩。相反，EIF导致组胺预收缩的主动脉环剂量依赖性舒张，类似于在大鼠主动脉环中观察到的情况。在两种物种中，EIF的舒张作用均被证明是内皮依赖性的且由一氧化氮介导，因为EIF诱导的舒张可被一氧化氮合酶抑制剂2微摩尔L- NAME抑制。阿托品（0.2微摩尔）或吲哚美辛（10微摩尔）对EIF诱导的豚鼠或大鼠主动脉平滑肌舒张均无显著影响。
