High renal plasma flow lability in the kidneys of hypertensive patients.

The spontaneous changes in renal plasma flow (RPF) were determined by sodium paraamino hippurate clearance (CPAH) in the individual kidneys of 71 patients with essential and secondary hypertension. These changes were expressed as changes in CPAH and as changes in CPAH per 100 ml Glomerular Filtration Rate (GFR = inulin clearance) for every individual kidney. Sixteen normal subjects were used as control. The RPF changes were measured between two consecutive 10 minute clearance periods during separated kidney function tests. In all the hypertensive groups studied, when RPF variability was expressed per 100 ml GFR, the variability was found to be two to five times greater than in normals. This findings suggests that in the hypertensive state the blood flow changes in the kidney are more labile than in normals. The high lability of renal blood flow could reflect and abnormality in renal vascular tone. This abnormality could be an important factor in the pathogenesis and maintenance of high blood pressure.