FIXED AND REPRODUCIBLE ORTHOSTATIC PROTEINURIA. III. EFFECT OF INDUCED RENAL HEMODYNAMIC ALTERATIONS UPON URINARY PROTEIN EXCRETION*

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Abstract
Differing renal hemodynamic patterns were produced in 48 patients by unmodified orthostasis, supine thigh tourniquet application, lower extremity positive-pressure while standing, and orthostasis after prior administration of hydralazine. The upright response of filtration rate (GFR), renal plasma flow (RPF) and filtration fraction (FF) did not differ from those described by others in normal subjects. Supine thigh tourniquet application reduced GFR and RPF but FF did not change; upright pressure support to the lower extremities was attended by maintenance of GFR and reduction of RPF. Proteinuria occurred during both maneuvers. Prior treatment with hydralazine prevented the usual upright fall of RPF and markedly depressed the typical rise of protein excretion during orthostasis. These findings suggest that the normal upright reduction of RPF is the most important hemodynamic determinant of erect proteinuria in patients with fixed and reproducible orthostatic proteinuria.