Role of nitric oxide in salt and water excretion in experimental hypertension in hooded (Aguti) rats.

OBJECTIVES

The present study was designed to investigate the suitability of the hooded rat in experimental hypertension studies and to investigate some mechanisms underlying the development of hypertension.

METHODS

Hooded rats were randomly divided into 4 groups: control, Salt, L-NAME (N' -Nitro-L-Arginine Methyl Ester) and salt+L-NAME. Control rats received a normal rat chow. Hypertension was induced in the test groups by giving 8% salt and/or 100mg/kg/day L-NAME for 6 and/or 4 weeks respectively. Urine and serum samples were collected from the rats and analysed for their cation contents. The blood pressure of the rats was measured.

RESULTS

The mean arterial pressure (mean +/- SEM; mm Hg) increased significantly in the test groups of rats (salt: 138.3+/-4.0; L-NAME: 165.7+/-6.0; salt+L-NAME: 133.35.2) when compared with control (88.42.7; P<0.05). Water consumption, urine volume and Na+ excretion increased significantly in salt-loaded and salt+L-NAME groups compared with control (P<0.05) but remained similar in L-NAME rats. These values were however significantly less in salt+L-NAME rats compared with salt loaded rats (P<0.05). Urinary K+ excretion, serum Na+ and K+ concentrations remained similar in all groups.

CONCLUSIONS

These results suggest that the hooded rat may be useful for experimental hypertension studies. Attenuation of the diuretic and natriuretic responses to salt loading in the presence of L-NAME suggests that nitric oxide is involved in the mechanisms involved in these responses. It is concluded that nitric oxide deficiency may exacerbate salt and volume retention in salt-loaded rats and possibly play a role in the subtle renal defect underlying salt sensitive hypertension.