Acute Cardiovascular Response to a Single Large Intravenous Dose of Methylprednisolone and Its Effects on the Responses to Norepinephrine and Isoproterenol

The cardiovascular actions of single 10-μg/kg iv doses of norepinephrine (NE) and isoproterenol (ISO), before and after the administration of a single 30-mg/kg iv dose of the glucocorticoid methylprednisolone (MP) (sodium succinate ester), were compared in adult cats. Methylprednisolone increased both systolic and diastolic pressures as well as the pulse pressure by approximately 50%. These steroid effects persisted unabated for the duration of the experiment (40 min). Heart rate was unaffected by MP. MP treatment significantly reduced the increase in systolic and diastolic pressures caused by NE. This MP effect was unrelated to the higher baselines for these two parameters caused by the steroid. The systolic blood pressure and positive chronotropic effects of ISO were also significantly blunted by MP. These observations suggest that a single large dose of MP may cause a depression of cardiovascular α- and β-1-receptor sensitivity. The results are discussed in relation to the actions of massive dose glucocorticoid administration in certain shock states and central nervous system trauma and stroke.