The Role of Intrarenal Vasoactive Substances in the Pathogenesis of Essential Hypertension

To investigate the role of renal vasoactive substances in the pathogenesis of essential hypertension, urinary prostaglandin E excretion, urinary kallikrein excretion, plasma renin activity, plasma aldosterone concentration and urinary Na excretion were measured in normal subjects and patients with essential hypertension after stimulation of the renin—angiotensin—aldosterone system by the intravenous injection of frusemide or a low Na diet; after the inhibition of renin—angiotensin—aldosterone by an angiotensin II antagonist and after the inhibition of renal prostaglandin E synthesis by indomethacin. The urinary excretions of prostaglandin E and kallikrein, plasma renin activity and plasma aldosterone concentration increased after frusemide administration. The urinary excretion of kallikrein increased after frusemide or a low Na diet but decreased after the angiotensin II antagonist and indomethacin during Na depletion. Changes in urinary kallikrein excretion paralleled those in the renin—angiotensin—aldosterone system after various stimuli. The urinary excretion of prostaglandin E increased after frusemide. However, a dissociation between the urinary excretions of prostaglandin E and kallikrein was found during the low Na diet: the former decreased and the latter increased. The urinary excretion of prostaglandin E was closely related to urinary Na output after various stimuli. Basal levels of urinary prostaglandin E and kallikrein excretion were lower in essential hypertension than in normal subjects. The release of renal prostaglandin E and kallikrein after frusemide was also suppressed in essential hypertension compared with that in normal subjects. The data indicate that renal kallikrein—kinin and renin—angiotensin—aldosterone may interact in a dynamic fashion to maintain blood pressure, that renal prostaglandin E may be involved in renal Na handling and that the suppression of renal kallikrein—kinin and prostaglandin E in essential hypertension may be an etiological factor in essential hypertension.