The influence of high salt intake and/or chronic blood volume expansion on renin-angiotensin system in Brattleboro rats.

The influence of chronic saline drinking and/or DOCA-salt treatment on plasma renin activity and renal renin concentration was studied in vasopressin-deficient homozygous (DI) Brattleboro rats and their vasopressin-secreting heterozygous (non-DI) littermates. The activity of renin-angiotensin system (RAS) can be suppressed even in the absence of vasopressin under the conditions of a sufficiently high salt intake that is achieved in DI rats by consumption of 0.6% saline instead of water. An almost complete RAS suppression in both plasma and kidney was observed in young animals in which high salt intake induced not only blood volume expansion but also blood pressure elevation, i.e. in mildly hypertensive unilaterally nephrectomized saline drinking DI rats as well as in moderately hypertensive DOCA-salt treated DI rats and in non-DI rats with a severe DOCA-salt hypertension. Our results indicate that intravascular expansion and blood pressure changes are important factors for the modulation of plasma and renal renin activity even in the absence of vasopressin.