Urinary Protein Excretion and Renal Hemodynamic Adjustments during Orthostasis in Patients with Acute and Chronic Renal Diseases12

Fixed and Reproducible Orthostatic Proteinuria. Iii. Effect of Induced Renal Hemodynamic Alterations Upon Urinary Protein Excretion*

“…Prior treatment with hydralazine during recumbency prevented the usual average reduction of PAH clearance upon standing, and the small rise of protein excretion that occurred was much less than that observed before drug treatment. 5. As in other patients with more severe glomerular defects, this combination of findings is compatible with the proposal that a normal reduction of renal blood flow during standing is the main hemodynamic determinant of upright protein excretion in patients with fixed and reproducible orthostatic proteinuria.…”

“…Regardless of whether vascular adjustments in this condition are normal or abnormal, several observers have emphasized their contribution to urinary protein excretion in both patients with orthostatic proteinuria and with overt forms of renal disease (5,6,24,25). General agreement has not been reached as to which renal hemodynamic parameter is of most importance in this regard.…”

“…A basis for this proposal is provided by previous observations in patients with more advanced alterations of glomerular anatomy due to obvious renal disease. Several observers have indicated that glomerular protein transfer may be conditioned by intrarenal hemodynamic adjustments to the erect posture (5,6). …”

RENAL CIRCULATORY DYNAMICS AND URINARY PROTEIN EXCRETION DURING INFUSIONS OF l-NOREPINEPHRINE AND l-EPINEPHRINE IN PATIENTS WITH RENAL DISEASE 12

“…Thus filtration may be modified under conditions which alter intraglomerular hydrostatic pressure (3)(4)(5) and diffusion under circumstances which influence the rate of formation of glomerular filtrate (2). It has been suggested that protein transport and urinary protein excretion may be altered by renal circulatory adjustments which modify the area available for transport within the kidney (6) or which influence the integrity of the capillary wall (7)(8)(9). Moreover, it has recently been suggested that protein transport may also be conditioned by the velocity of blood flow through the glomerulus (10).…”

Methods Used for the Analysis of Proteins in the Urine

“…Firstly, there is a large sample-to-sample variation in the amount and composition of the urine proteins. Albumin excretion can vary from as little as 20 mg/day or less in the normal [45,58] to 20 g/day or more in a patient with the nephrotic syndrome [36]. Since many analytical methods are limited in the range over which they function, additional preparative steps may be needed before analysis is possible, and all samples cannot always be analyzed in the same manner.…”