EFFECTS OF LOSARTAN ON RENAL-FUNCTION IN PATIENTS WITH ESSENTIAL-HYPERTENSION

We examined the renal hemodynamic modifications induced by a selective angiotensin II (AII) ATI receptor antagonist, losartan, in 10 patient s with essential hypertension. In this single-blind study, renal hemod ynamic parameters were determined twice (patients were their own contr ols) first after a 15-day single-blind placebo run-in period and again after a 1-month losartan period. The dosage of losartan was 50 mg/day . Glomerular filtration rate (GFR, inulin clearance), renal plasma flo w [RPF; pala-aminohippurate (PAH) clearance], microalbuminuria, sodium excretion, proximal sodium tubular reabsorption (lithium clearance), and acid uric metabolism were measured. After 1-month losartan treatme nt, systolic and diastolic BP (SEP, DBP) decreased significantly throu ghout the 210-min recording whereas heart rate (HR) was unchanged. GFR (100 +/- 19 vs. 96 +/- 17 ml/min/1.73 m(2)) and RPF (471 +/- 118 vs. 468 +/- 108 ml/min/1.73 m(2)) were not altered by losartan. Rather tha n occurrence of any modification in filtration fraction (FF), a signif icant decrease in microalbuminuria was evident (57 +/- 77 vs. 40 +/- 5 9 mg/24 h, p < 0.05), Urinary sodium excretion was not modified, but a n almost significant (p 0.07) decrease in proximal sodium reabsorption was observed (72.9 +/- 7.7 vs. 68.1 +/- 6.4% of filtered sodium). The increase in renal uric clearance accounted for the significant decrea se in serum uric acid (195 +/- 49 vs. 183 +/- 43 mu M; p < 0.05). Afte r 1-month losartan treatment, renal function was well preserved; the d ecrease in uric acid may be of clinical interest when adjuvent diureti c therapy is required.