Bailey J R, Driedzic W R
Department of Biology, Mount Allison University, Sackville, Canada.
J Exp Zool. 1997 Aug 1;278(5):273-82. doi: 10.1002/(sici)1097-010x(19970801)278:5<273::aid-jez1>3.0.co;2-m.
An earlier study determined that protein synthesis in isolated perfused turtle (Trachemys [= Pseudemys] scripta elegans) hearts was three-fold lower under conditions of anoxia than under conditions of normoxia. However, the earlier study did not attempt to define the role of work in the isolated perfused preparation. In this study, the effects of varying workload, as defined by changing frequency of contraction, and anoxia on protein synthesis were examined. The ventricle strip preparation allows for comparison of multiple strips from a single heart, which aids in eliminating the variability found between individuals chosen from wild populations. Ventricle strips forced to contract at 24 contractions.min-1 under anoxic conditions failed more rapidly than strips forced to contract at 24 contractions.min-1 under normoxic conditions. Protein synthesis decreased by 32% when compared to normoxic controls. When stimulation was terminated after 2 hr of contraction, the rate of protein synthesis in strips under anoxic conditions was similar to that in strips under normoxic conditions. Also, returning strips to normoxic conditions after 2 hr of anoxia restored protein synthesis to the level of the normoxic controls. A significant correlation between pacing rate and protein synthesis was found under normoxic conditions but not under anoxic conditions when strips were paced at 12, 18 and 24 contractions.min-1. Protein synthesis increased by 30% at the 18 contractions.min-1 frequency and 45% at the 24 contractions.min-1 frequency over the rate at 12 contractions.min-1 frequency. Force-frequency studies revealed that under normoxic conditions force generation did not change until above 24 contractions.min-1, but under anoxic conditions there was a significant negative inotropic effect (20% decrease in force) at 24 contractions.min-1 and fell to 50% of initial at 36 contractions.min-1. These studies indicate that, in the turtle heart, anoxia per se is not the only determinant of protein synthesis but rather that work plays an important role in protein synthesis, as in the mammalian heart.
一项较早的研究确定，在缺氧条件下，离体灌注的乌龟（滑龟[=彩龟]指名亚种）心脏中的蛋白质合成比在常氧条件下低三倍。然而，较早的研究并未尝试确定功在离体灌注标本中的作用。在本研究中，研究了由收缩频率变化定义的不同工作量以及缺氧对蛋白质合成的影响。心室条带标本允许比较来自单个心脏的多个条带，这有助于消除从野生种群中选取的个体之间存在的变异性。在缺氧条件下被迫以每分钟24次收缩进行收缩的心室条带比在常氧条件下被迫以每分钟24次收缩进行收缩的条带更快地衰竭。与常氧对照相比，蛋白质合成下降了32%。当收缩2小时后终止刺激时，缺氧条件下条带中的蛋白质合成速率与常氧条件下条带中的相似。此外，缺氧2小时后将条带恢复到常氧条件可使蛋白质合成恢复到常氧对照水平。当条带以每分钟12次、18次和24次收缩进行起搏时，在常氧条件下发现起搏速率与蛋白质合成之间存在显著相关性，但在缺氧条件下未发现。与每分钟12次收缩频率相比，在每分钟18次收缩频率时蛋白质合成增加了30%，在每分钟24次收缩频率时增加了45%。力-频率研究表明，在常氧条件下，直到高于每分钟24次收缩时力的产生才会改变，但在缺氧条件下，在每分钟24次收缩时存在显著的负性肌力作用（力降低20%），在每分钟36次收缩时降至初始值的50%。这些研究表明，在乌龟心脏中，缺氧本身不是蛋白质合成的唯一决定因素，而是功在蛋白质合成中起重要作用，就像在哺乳动物心脏中一样。
