Plasma renin activity and renal sodium and water excretion following infusion of arachidonic acid in rats.
Plasma renin activity (PRA) and urinary sodium and water excretion were measured following infusion of the prostaglandin (PG) precursor arachidonic acid (C20:4) in normal hydrated rats (saline i.v.:0.5 ml/hr/100 g body weight) and in rats with moderate volume expansion (saline i.v.:1.5 ml/hr/100 g body weight). Nonhypotensive doses of C20:4(40-70 mu/min/100 g b.w.) increased PRA in both normal and volume-expanded rats (p less than 0.05, and p less than 0.025, respectively). In volume-expanded rats, C20:4 was followed by reduced lrine volume (p less than 0.01) and sodium excretion (p less than 0.001) in comparison to volume-expanded control rats, whereas in normal hydrated rats these parameters remained unchanged after C20:4. The present results indicate that the C20:4-stimulated PG-synthetase system can increase PRA independently of the extracellular fluid volume. Furthermore, these results suggest a complex interrelationship between PG-synthetase action, activation of the renal renin-angiotensin system and urinary water and sodium excretion.