Loss of cardiac contractility and severe morphologic changes by acutely lowering the pH of the perfusion medium: protection by fatty acids.

When the pH of the perfusion medium of rat Langendorff heart, paced at a rate of 300 beats/min, is abruptly lowered from pH 7.5 to 7.0, the hearts stop beating within 6 min in more than half of the cases. Reperfusion with pH 7.5 medium after 10 min pH 7.0 perfusion does not cause contractility to resume within 5 min. The causative factor is intracellular acidosis, resulting in severe morphological alterations of plasma membrane and mitochondria. It is probably initiated by the loss of membrane-bound calcium. Oleate, complexed with albumin included in the perfusion media, protects the hearts. This may be explained by maintenance of capillary flow and limitation of cellular acidosis.