Spontaneous variations in renal vein renin activity in man

The spontaneous variations in renal vein renin activity (RVRA) and in peripheral vein renin activity (PVRA) were studied in one normotensive and nine hypertensive patients. Eight of the hypertensive patients had renal artery stenosis on one or both sides. Blood samples were drawn simultaneously from the two renal veins and from a peripheral vein every fifth or tenth minute for one hour. Plasma renin activity (PRA) was measured by radioimmunoassay. The precision of the PRA assay, expressed as coefficient of variation, was related to the PRA level. A large intra-individual variations was found in RVRA, the RVRA ratio and PVRA even in patients with unilateral renovascular hypertension. The intra-individual variation could not be explained by specimen collection error or by error of the assay procedure. The variation seems to be reflect a biological fluctuation. The clinical implication of these findings is that repeated, simultaneous collection from the two renal veins, avoidance of factors known to decrease renin secretion. and consideration of the relation between the RVRA ratio and RVRA level are of importance in the preoperative evaluation of patients with renal artery stenosis.