HIGH SODIUM-INTAKE DECREASES PRESSURE-INDUCED (MYOGENIC) TONE AND FLOW-INDUCED DILATION IN RESISTANCE ARTERIES FROM HYPERTENSIVE RATS

High sodium intake has been associated with a higher blood pressure le vel. Resistance arteries are the main determinants of blood pressure. They are largely regulated by pressure (tensile stress)-induced tone ( myogenic tone, MT) and by flow (shear stress)-induced dilation (FD). T hus, we studied the effect of NaCl (8%) intake for 8 weeks on FD and M T in mesenteric resistance arteries of spontaneously hypertensive rats . Arteries were cannulated and mounted in an arteriograph. Intralumina l diameter was measured continuously. High NaCl intake increased mean arterial pressure (186+/-5 to 217+/-6 mm Hg, P<0.01). Passive arterial diameter ranged from 112+/-6 to 185+/-9 mu m (pressure from 25 to 125 mm Hg, no effect of NaCl), MT developed in response to pressure (tone from 89+/-1% to 83+/-3% of passive diameter, 25 to 125 mm HE). High N aCl intake significantly decreased MT (89+/-1% versus 83+/-3% of passi ve diameter when pressure was 125 mm Hg, P<0.023). High NaCl intake al so decreased FD (6.5+/-0.8 versus 10+/-1.3 mu m dilation under a press ure of 100 mm Hg and a flow rate of 160 mu L/min, P<0.012). Thus, high salt intake decreased both flow (shear stress)-induced dilation and p ressure (tensile stress)-induced tone in mesenteric resistance arterie s. These findings might reflect attenuation by NaCl of flow and pressu re mechanosensor processes.