Depressor systems contribute to hypertension induced by glucocorticoid excess in dogs

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Objective:The aim of this study was to investigate the role of depressor systems in glucorticoid-induced hypertension.Methods:The serial changes in cardiorenal hemodynamics, urinary excretions of kallikrein and prostaglandins (PGE2 and the prostacyclin derivative 6-keto-PGF) before, and during the administration of both low and high doses of dexamethasone (9 α-fluoro-16 α-methylprednisolone) and after the cessation of dexamethasone were examined in conscious trained dogs. In addition, pressor responses to prostaglandin, bradykinin, bradykinin antagonist and indomethacin were studied during the administration of dexamethasone.Results:High-dose dexamethasone induced a significant elevation in mean arterial pressure (MAP) that was accompanied by a significant reduction in the urinary excretion of kallikrein, PCE2 and 6-keto-PCF. In contrast, low-dose dexamethasone treatment had no significant effect upon MAP but induced a transient elevation in the urinary excretion of kallikrein, PGE2 and 6-keto-PGF. Furthermore, additional oral administration of indomethacin produced a significant elevation in MAP in dogs treated with low-dose dexamethasone, but did not affect the hemodynamics of animals with high-dose dexamethasone. Whilst i.v. administration of either bradykinin or prostacyclin induced a significant reduction in MAP in high-dose but not low-dose dexamethasone-treated dogs, administration of a competitive bradykinin antagonist, D-Arg-[Hyp3, Thi5,8, D-Phe7]-bradykinin induced a significant elevation in MAP in low-dose but not high-dose dexamethasone-treated dogs.Conclusion:Depressor systems play an important role in regulation of blood pressure in glucocorticoid-treated dogs.

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