PS-B10-8: BLOCKADE OF AT1 RECEPTORS RESTORE P2/P1 WITHOUT CHANGING INTRACRANIAL PRESSURE IN RENOVASCULAR HYPERTENSIVE RATS WITH 0.3 M NACL AD LIBITUM

Abstract

Objective: Renovascular hypertension is characterized by activation of the renin angiotensin aldosterone system, elevated sympathetic nerve activity and sodium appetite behavior. The association of increased sodium intake and hypertension can worsen the injury to end organs. We tested the effects of AT1 receptors blockade (losartan, 10 mg/kg iv) on mean arterial pressure (MAP), intracranial pressure (ICP) and P2/P1 ratio (index of brain compliance) in 2K1C rats with 0.3 M NaCl ad libitum. Design and Methods: Male Holtzman rats (150 tp 180 g) with water and food ad libitum received a silver clip around the left renal artery to induce 2K1C or no clip (SHAM surgery) resulting 3 groups: SHAM (n = 9), 2K1C (n = 9) and 2K1C/Na (n = 7), which had an additional bottle of 0.3 M NaCl ad libitum. Six weeks after the renal surgery, MAP and ICP were recorded under urethane anesthesia (1.2 g/kg iv) and the P2/P1 was calculated offline from the waveform. Saline (0.2 ml/rat) was used as control injection before losartan. Results: In SHAM rats, ICP and P2/P1 were not changed by losartan (7.8 ± 1.1 and 0.88 ± 0.02; vs. saline: 7.9 ± 1.1 and 0.83 ± 0.01 mmHg, respectively), while MAP was decreased (104 ± 5, vs. saline: 120 ± 3 mmHg, p < 0.05). In 2K1C, MAP, ICP and P2/P1 values were greater than SHAM (respectively, 196 ± 6, 14.7 ± 2.7 and 1.1 ± 0.03 mmHg, vs. SHAM; p < 0.05) and all of them were decreased by losartan pre-treatment (137 ± 6, 8.6 ± 1.3 and 0.87 ± 0.05 mmHg, vs. saline, respectively). In 2K1C-Na MAP and P2/P1 were greater than in SHAM (186 ± 7 and 1.15 ± 0.06 mmHg, vs sham p < 0.05) and were decreased by losartan (162 ± 8 and 0.87 ± 0.02 mmHg, vs. saline; p < 0.05), although the decrease in MAP after losartan was lesser than the observed in 2K1C rats (p < 0.05). In 2K1C-Na rats, ICP was not different from SHAM (10.8 ± 1.2, vs. SHAM: 7.8 ± 1.1 mmHg, p > 0.05) and losartan had no effect on ICP (10.3 ± 1.7, vs. saline: 10.8 ± 1.2 mmHg, p > 0.05). Conclusion: Even without a change in ICP, AT1 blockade in 2K1C-Na was effective in restoring P2/P1 ratio, suggesting a beneficial effect on brain compliance in this situation.