Adequacy of oxygenation of isolated perfused rat heart.

Detailed arguments are presented for the adequacy of oxygenation of the isolated perfused rat heart preparation when subjected to a work load according to the model of Neely. Lactate discharge from a heart perfused with glucose does not equal hypoxia (although lactate output is a prime sign of hypoxia in the heart in situ where numerous other substrates are available). Adequacy of oxygenation does not mean normality of oxygenation. There is still an outstanding question as to whether the high oxygen tensions might not promote lipid peroxide formation, thereby sensitizing the hearts to the potentially harmful effects of fatty acids. Bearing in mind the above reservations, the isolated perfused heart model has made major contributions to the study of normal myocardial metabolic patterns. Such a rapid pace of advance would not have been possible without the use of the Krebs-Henseleit bicarbonate buffer medium.