Methylprednisolone reduces vascular resistance in hypoxic and atelectatic lungs

The effect of pharmacological doses of methylprednisolone (MP) on the pulmonary vasoconstrictor response to hypoxia has been investigated in two groups of isolated rat lung preparations, one consisting of ventilated, and the other of atelectatic lungs. In both groups, MP reduced the vasoconstrictor response to hypoxia in a dose-dependent fashion. At a perfusate concentration of 3 mmol/l of MP, the response was reduced by about 80%. On the contrary, the vasoconstrictor response to injections of standardized doses of angiotensin II, used as an independent vasoconstrictor substance, were not significantly changed by MP, even when administered at a concentration which completely abolished the response to hypoxia. We suggest that MP inhibits the pulmonary vasoconstrictor response to hypoxia without influencing the general reactivity of the pulmonary vascular bed.