RENAL ABNORMALITY OF ESSENTIAL HYPERTENSION

Although homœostatic mechanisms relate sodium balance, renin, and arterial pressure, the reduction of renin sometimes seen in essential hypertension cannot be attributed to abnormal sodium retention. It is proposed instead that renin decreases and sodium status remains normal because the pressure-natriuretic mechanism within the kidney is reset by increased filtration fraction. Neurogenic factors may raise blood-pressure and cause resetting by some other means at an early (labile) stage of essential hypertension, but, once filtration fraction is raised and remains elevated on withdrawal of the neurogenic component, essential hypertension will have a renal cause. A similar mechanism may account for the failure of secondary hypertension to fall when its cause is removed.