1. Partial replacement of sodium by potassium in the diet attenuates the rise in blood pressure in stroke-prone spontaneously hypertensive rats (SHR-SP).
2. The blood pressure-lowering effect of potassium cannot be ascribed to a reduction in intravascular volume.
3. The increased dietary intake of potassium leads to a reduced stimulation of the sympathoneuronal and sympathoadrenal system by cold compared with the response of sodium-loaded rats.
4. The impaired inactivation of noradrenaline observed in sodium-loaded SHR-SP is improved in SHR-SP on a potassium-substituted diet.
5. It is concluded that changes in dietary intake of sodium and potassium modulate sympathetic activity and the metabolism of noradrenaline, both of which are related to the development of hypertension in SHR-SP.