The restorative effect of apocynin and catalase in l-arginine induced hypotension on normotensive subjects - the role of oxidative stress

Abstract

L-arginine is a substrate for nitric oxide synthase (NOS) responsible for the production of NO. This investigation studied the effect of apocynin, an NADPH oxidase inhibitor and catalase, an H2O2 scavenger on L-arginine induced oxidative stress and hypotension. Forty Wistar-Kyoto rats were treated for 14 days with vehicle, L-arginine (12.5mg/ml p.o.), L-arginine+apocynin (2.5mmol/L p.o.), L-arginine+catalase (10000U/kg/day i.p.) and L-arginine plus apocynin+catalase respectively. Weekly renal functional and hemodynamic parameters were measured and kidneys harvested at the end of the study for histopathological and renal NADPH oxidase 4 (Nox4) assessments. L-arginine administration in normotensive rats decreased systolic blood pressure (120±2 vs 91±2mmHg) and heart rate (298±21 vs 254±15b/min), enhanced urinary output (21.5±4.2 vs 32±1.9ml/24h , increased creatinine clearance (1.72±0.56 vs 2.62±0.40ml/min/kg), and fractional sodium excretion (0.88±0.16 vs 1.18±0.16 %), caused proteinuria (28.10±1.93 vs 35.26±1.69mg/kg/day) and a significant decrease in renal cortical blood perfusion (292±3 vs 258±5bpu) and pulse wave velocity (3.72±0.20 vs 2.84±0.13m/s) (all P<0.05). L-arginine increased plasma malondialdehyde (by ~206 % P<0.05) and NO (by~51 %, P<0.05) but decreased superoxide dismutase (by~31 %, P<0.05) and total antioxidant capacity (by~35 %, P<0.05) compared to control. Renal Nox4 mRNA activity was approximately 2.1 fold higher (P<0.05) in the L-arginine treated rats but was normalized by apocynin and apocynin plus catalase treatment. Administration of apocynin and catalase, but not catalase alone to rats fed L-arginine, restored the deranged renal function and structure, prevented hypotension and enhanced the antioxidant capacity and suppressed Nox4 expression. These findings suggest that apocynin and catalase might be used prophylactically in states of oxidative stress.

Fig. 1

Biochemical analysis of oxidative stress markers. Plasma levels of MDA (A), T-SOD activity (B), NO (C) and total AOC (D) were measured in control (C-Veh), L-arginine treated (L-arg), L-arginine treated with apocynin (L-argApo), L-arginine treated with catalase (L-argCat) and L-arginine treated with apocynin plus catalase (L-argApoCat) rats. Data presented as mean±SEM on Day 14. ¥ p<0.05 vs. C-Veh of all except L-arg; # p<0.05 vs. C-Veh; † p<0.05 vs. L-arg; p<0.05 vs. L-argApoCat; δ p<0.05 vs. L-argApo.

Fig. 2

The molecular expression of Nox 4 mRNAs activity in the renal tissue homogenate of control (C-Veh), L-arginine-treated (L-arg), L-arg treated with apocynin (L-argApo), L-arg treated with catalase (L-arg Cat) and L-arg treated with apocynin plus catalase (L-argApoCat) rats. Data presented as mean ± SEM on Day 14. ¥ p<0.05 vs. C-Veh of all except L-arg; # p<0.05 vs. C-Veh; † p<0.05 vs. L-arg; p<0.05 vs. L-argApoCat; δ p<0.05 vs. L-argApo.

Fig. 3

Histopathological study of rat renal tissue. The renal tissue of C-Veh [A], L-argApo [C] and L-argApoCat [F] rats showed normal glomerular and tubular structures. However, there was a prominent mild arteriolar constriction found in the glomeruli (open arrow) and a mild ischemic damage in the tubular area (solid arrow) in the kidney of L-arg rats [B]. Similarly, a mild arteriolar congestion (open arrow) in the glomeruli [D] and a minimal ischemic tubular congestion (solid arrow) was also manifested in the renal tissue of L-argCat rats [E]. (Hematoxylin and eosin stain; original magnification ×10)