Role of L-arginine in the modulation of physical parameters and myocardial oxygen demand in salt-induced hypertension in Sprague-Dawley rats

Abstract

Background: High blood pressure and myocardial oxygen demand have been shown to have positive correlation with the severity of cardiovascular disease. Although L-arginine is a known vasodilator, the role it plays in the modulation of physical parameters and myocardial oxygen demand in hypertension is not clearly understood.

Objectives: This study sought to investigate the role of oral L-arginine supplementation in the modulation of physical parameters and myocardial oxygen demand in saltinduced hypertension.

Methods: Forty-eight (48) weanling 6 weeks old Sprague- Dawley (SD) rats of body weights 50-60g were divided into 6 groups of 8 rats each. Group I was fed with normal rat chow containing 0.3% NaCl. Group II was fed with high salt diet containing 8% NaCl. Groups III and IV were fed normal and high salt diet respectively then supplemented with Larginine (100mg/kg/day) while groups V and VI were fed normal and high salt diet respectively then co-administered with both L-arginine and L-NAME (100mg/kg/day and 40mg/kg/day respectively). Blood pressure parameters were determined via left carotid artery cannulation. Rate pressure product (RPP) was calculated and used as an index of myocardial oxygen demand. Heart and kidney weights were also measured.

Results: Salt-loading caused significant (p<0.05) loss of weight in the rats. It also significantly (p<0.05) increased heart and kidney weight indices as well as the RPP. Supplementation of the salt-loaded rats with L-arginine reduced significantly (p<0.05) heart and kidney weight indices. Supplementation with L-arginine also caused reduction in RPP without causing significant change in body weight of the salt-loaded rats. Co-administration of LNAME with L-arginine however caused reversal of some of the ameliorating effects of L-arginine supplementation.

Conclusion: In conclusion, results from this study suggest that oral supplementation of L-arginine reversed heart hypertrophy, renal hypertrophy and high myocardial oxygen demand in male SD rats fed a high salt diet.

Keywords: L-arginine, heart index, kidney index, myocardial oxygen demand, rate pressure product