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Pentobarbital sodium is a widely used anesthetic for animal experiments. We have already reported that a high dose of pentobarbital sodium (100 mg/kg i.p., twice the usual anesthetic dose) depresses myocardial mechanoenergetics in the canine heart. Furthermore, it has been reported that a high concentration of pentobarbital sodium inhibits myocardial contractility and mitochondrial electron transport and energy transfer. Therefore, we were afraid that the mitochondrial respiratory function would be impaired by pentobarbital anesthesia and that pentobarbital sodium would be an inappropriate anesthetic for cardiac mechanoenergetic studies. In this study, we investigated the respiratory function of mitochondria isolated from the hearts of anesthetized rats with high-dose pentobarbital sodium. We examined the mitochondrial respiratory function by the ADP/O ratio, respiratory control index (RCI), oxygen consumption rate in state III (State III O2) by oximetry, and membrane potential using a fluorescent dye, 3,3'-dipropylthiodicarbocyanine iodide (diS-C3-(5). The ADP/O ratio, RCI, and State III O2 values and changes in membrane potential induced by various respiratory substances were not significantly different between the rats with and without anesthesia. These results indicate that the respiratory function is not suppressed in the isolated myocardial mitochondria of rat hearts after high-dose pentobarbital anesthesia, although the pentobarbital sodium blood concentration was of the same order as that which exerts mitochondrial uncoupling in rat isolated mitochondrial preparation. Therefore, pentobarbital sodium anesthesia up to 100 mg/kg i.p. is applicable for mechanoenergetic studies of excised rat hearts, at least from the energetic aspect.
Takaki et al. (Wed,) studied this question.