[Effect of spironolactone on L-arginine/iNOS/NO pathway of aortic adventitia in spontaneously hypertensive rats].

OBJECTIVE: Adventitia plays an important role in vascular injury diseases. Nitric oxide (NO) from inducible nitric oxide synthase (iNOS) is involved in many cardiovascular diseases. iNOS/NO pathway is activated in aorta of spontaneously hypertensive rats (SHRs). The role of aldosterone in L-arginine (L-Arg)/iNOS/NO pathway of aortic adventitia is uncertain. We investigated the effect of aldosterone antagonist spironolactone on adventitial L-Arg/iNOS/NO pathway in SHRs. METHODS: Twenty male SHR (10 weeks old, 220-280 g) were randomly divided into 2 groups (10 in each): untreated or treated with the aldosterone receptor antagonist, spironolactone (20 mg/kg per day) for 6 weeks. Age-matched Wistar-Kyoto rats (WKY) were used as control. Systolic blood pressure (tail-cuff method) was measured weekly. Six weeks later, the rats were sacrificed. The whole aorta was collected and aortic adventitia was isolated. iNOS activity, [(3)H]-L-Arg transport assay of aortic adventitia were carried out by isotope-labeled L-arginine conversion rate measurement, and measurement of nitrate/nitrite (NOx), an index of NO production of aortic adventitia was assayed with the Griess reaction. RESULTS: iNOS activity, [(3)H]-L-Arg transport and NO production were greatly increased in aortic adventitia of SHR [(12.55 +/- 2.27) pmol x mg(-1) x min(-1), (0.88 +/- 0.19) pmol x mg(-1) x min(-1) and (2.07 +/- 0.39) micromol/L)] compare versus WKY [(5.96 +/- 1.87) pmol x mg(-1) x min(-1), (0.51 +/- 0.15) pmolxmg(-1) x min(-1) and (1.55 +/- 0.32) micromol/L, P < 0.01], and decreased significantly by spironolactone treatment [(8.32 +/- 1.84) pmol x mg(-1) x min(-1), (0.61 +/- 0.15) pmol x mg(-1) x min(-1) and (1.64 +/- 0.27) micromol/L, P < 0.01]. CONCLUSION: L-Arg/iNOS/NO is activated in aortic adventitia of SHR. Spironolactone can inhibit the activation of L-Arg/iNOS/NO pathway. Aldosterone may play an important role in some cardiovascular diseases such as atherosclerosis through iNOS/NO pathway.

[Effects of aldosterone on inducible nitric oxide synthase/nitric oxide pathway in aortic adventitia].

OBJECTIVE: To evaluate the effect and related mechanisms of aldosterone (ALD) on inducible nitric oxide synthase (iNOS) activity and nitric oxide (NO) production in aortic adventitia. METHODS: Aortic adventitias from SD rats were incubated for 6 hours with various protocols: buffer alone (control), ALD (10(-8) mol/L - 10(-6) mol/L), ALD + spironolactone (10(-5) mol/L, ALD + SP), ALD + RU486 (10(-5) mol/L), LPS 10 ng/ml (LPS), ALD + LPS (10 ng/ml), ALD + LPS + SP (10(-5) mol/L), and ALD + LPS + RU486. Nitrate/nitrite (NOx), an index of NO production, was measured by Greiss Reaction. iNOS activity was determined by isotope-labeled L-arginine convertion rate. RESULTS: (1) NOx production and iNOS activity were similar between ALD and control groups (P > 0.05). NOx production was significantly reduced while iNOS activity remained unchanged in the ALD (10(-6) mol/L) + SP group compared to ALD (10(-6) mol/L) group. NOx production by 10(-7) mol/L and 10(-6) mol/L ALD increased by 50.0% and 58.7% respectively (P < 0.01) and iNOS activity was also significantly increased (P < 0.01) in ALD + RU486 group than that in ALD group. (2) LPS significantly increased the NOx production and iNOS activity (P < 0.01) and these effects were not augmented by adding ALD to LPS (P > 0.05) and SP significantly blocked and RU486 significantly enhanced the effects by LSP and ALD on NOx production and iNOS activity (P < 0.05). CONCLUSION: Aldosterone has a dual effect on iNOS/NO through mineralocorticoid receptor and glucocorticoid receptor pathway.