Pharmacological protection of mitochondrial function in hypoxic heart muscle: Effect of verapamil, propranolol, and methylprednisolone

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Abstract
Experiments were undertaken to determine if drugs (verapamil, propranolol, and methylprednisolone sodium succinate) that protect the fine ultrastructure of heart muscle against damage caused by hypoxia, protect mitochondrial function. Mitochondrial function was assessed in terms of oxidative phosphorylating and Ca2+-accumulating activities. Isolated rabbit hearts were used, and hypoxic conditions induced by reducing the perfusate Po2 from 80.0 to 0.80 kPa (600 to 6 mmHg). The drugs were either added at the start of the hypoxic perfusion or (verapamil and propranolol) the rabbits were pretreated with them. Verapamil, propranolol and, to a lesser extent, methylprednisolone sodium succinate, provided protection evidenced by the maintainance of near normal mitochondrial oxidative phosphorylating and Ca2+-accumulating activities after 60 min hypoxic perfusion. When added directly to mitochondria isolated from hypoxic-perfused muscle, the drugs had no effect.