Effect of 9-alpha-fluorohydrocortisone on forearm venous responses to norepinephrine and tyramine.

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Abstract
Forearm venous responses to norepinephrine and to tyramine were studied in 7 subjects treated for 1 week with 9[alpha]-fluorohydrocortisone, 1 mg initially and 0.2 mg daily. The drug was given orally. Control observations were made 3 weeks after stopping treatment. Venous tone was calculated from measurements of forearm volume at a transmural venous pressure of 30 mm Hg during brachial artery infusions of norepinephrine in doses of 0.0375, 0.075, and 0.15 [mu]g/ min and tyramine in doses of 9, 18, and 36 [mu]g/min. The ratio of the dose of norepinephrine which gave a certain venous response during the control period to the dose which gave the same response after treatment with 9[alpha]-fluorohydrocortisone was 1.442. The corresponding ratio for tyramine was 1.453. In these experiments the effects of norepinephrine and tyramine were potentiated by treatment with 9[alpha]-fluorohydrocortisone. This potentiation did not appear to be related to an effect of the steroid on endogenous norepinephrine stores since the responses to both norepinephrine and tyramine were increased by the same magnitude.