Different-efferent vessel dysfunction appears to be a specific characteristic of a large subset of patients with essential hypertension

Exercise renography makes it possible to subdivide essential hypertensives (EHs) into two distinct populations. Fifty to 60% develop exercise-mediated renal dysfunction and a transitory, severe reduction of glomerular filtrat ion. The other subset of EHs does not have exercise-mediated renal dysfunct ion. We hoped to learn whether the disturbance is also present while EHs re st. Twenty-six EHs and 21 normotensive controls were studied with a resting sequential renogram using Tc-99m-mercaptoacetyl-triglycine (MAG(3)), a tra cer excreted primarily by proximal tubular cells. EHs also had an exercise renogram. All persons had three consecutive 10-min dual-tracer infusion cle arance determinations with In-111-DTPA and I-131-hippurate, for the simulta neous determination of glomerular filtration rate (GFR) and effective renal plasma now (ERPF). To demonstrate the accuracy of the clearance procedure we sought to reproduce Hollenberg's results which show greater now variabil ity in EH than in normotension. Following this, the variability (VAR) of th e GFR and ERPF as well as the variability fraction (VF), the ratio of GFR v ariability divided into the ERPF variability, were calculated. Hollenberg's results were reproduced. Sixteen of 26 essential hypertensives developed e xercise-mediated renal dysfunction. GFR-VAR in EH differed from controls. T he VF suggests that EHs with a bilateral abnormal exercise renogram have a more pronounced GFR variability than those EH with a normal exercise renogr am. The results point to intraglomerular pressure fluctuations in patients with EH, and the VF suggests that this may be more pronounced in EHs with a bilateral abnormal exercise renogram than in those with a normal exercise renogram. It is hypothesized that the variable GFR provokes renin secretion in EH. (C) 2000 American Journal of Hypertension, Ltd.