RENAL HEMODYNAMIC-RESPONSES TO DYNAMIC EXERCISE IN RABBITS

Cardiovascular hemodynamics, including renal blood flow, were measured in rabbits with one intact and one denervated kidney during various i ntensities of treadmill exercise. Within the first 10 s of exercise, t here was rapid vasoconstriction in the innervated kidney associated wi th decreases in renal blood flow (range -10 to -17%). The vasoconstric tion in the innervated kidney was evident at all workloads and was int ensity dependent. There was no significant vasoconstriction or change in renal blood flow (range 0.5 to -3.1%) in the denervated kidney at t he onset of exercise. However; a slowly developing vasoconstriction oc curred in the denervated kidney as exercise progressed to 2 min at all workloads. Examination of responses to exercise performed under oc-ad renergic blockade with phentolamine (5 mg/kg iv) revealed that the vas oconstriction in the innervated kidney at the onset of exercise and th e delayed vasoconstriction in the denervated kidney were due primarily to activation of a-adrenergic receptors. In addition, a residual vaso constriction was also present in the innervated kidney after ol-adrene rgic blockade, suggesting that, during exercise, activation of other r enal vasoconstrictor mechanisms occurs which is dependent on the prese nce of renal nerves.