Spontaneously hypertensive rats (SHR) are sensitive to a high salt intake and we investigated the question of whether flow-induced dilation is affected by this type of diet, as flow responses are especially sensitive to small changes in extracellular sodium concentrations.Methods
We evaluated the effects of a diuretic (indapamide, 1.5 mg/kg per day, 8 weeks) on four groups of SHR (n = 42). One group was fed with a normal-salt diet (0.4%, control group, n = 10), the second with a high-sodium diet (8%, n = 12), the third with a high-sodium diet and indapamide (1.5 mg/kg per day, 8% salt, n = 10) and the fourth group was fed with indapamide alone (1.5 mg/kg per day, n = 10). The response to flow was studied in mesenteric resistance arteries (146 ± 6.1 μm internal diameter, pressure 100 mmHg) cannulated in vitro in an arteriograph.Results
The increase in mean arterial pressure (from 186 ± 4 to 218 ± 6 mmHg; P < 0.01) and heart weight: body weight ratio (3.48 ± 0.09 versus 4.34 ± 0.1 mg/g; P < 0.01) caused by the high salt intake was prevented by indapamide. A high salt intake significantly decreased flow-induced dilation (6 ± 0.8 versus 10.7 ± 1.2 μm dilation with a flow of 160 μl/min; P < 0.05), while indapamide significantly prevented the decrease in flow-induced dilation in high-salt SHR. Indapamide had no significant effect on flow-induced dilation in mesenteric resistance arteries from SHR with a normal-salt diet.Conclusions
Indapamide prevented the decrease in flow-induced dilation caused by a high-salt diet. Therefore, indapamide might counteract the disturbance in sodium-sensitive flow sensor(s), through a diuretic effect.