Effects of angiotensin II on renal dopamine metabolism: synthesis, release, catabolism and turnover.

Background/aims: Dopamine (DA) uptake inhibition in the renal cortex, elicited by angiotensin II (ANG II), is mediated by AT(1) receptors and signals through the phospholipase C pathway and activation of protein kinase C and CaM-kinase II. By this indirect way, ANG II stimulates renal Na(+),K(+)-ATPase activity through DA intracellular reduction. In the present work, we continued to study different aspects of renal DA metabolism in DA-ANG II interaction, such as DA synthesis, release, catabolism and turnover.

Methods: ANG II effects on DA synthesis, release, catabolism and turnover were measured in samples from the outer renal cortex of Sprague-Dawley rats.

Results: ANG II reduced renal aromatic acid decarboxylate activity without affecting basal secretion of DA or its KCl-induced release. Moreover, ANG II enhanced monoamine oxidase activity without altering catechol-o-methyl transferase activity and increased DA turnover.

Conclusion: Current results as well as previous findings show that ANG II modifies DA metabolism in rat renal cortex by reducing DA uptake, decreasing DA synthesis enzyme activity and increasing monoamine oxidase activity, and DA turnover. Together, all these effects may reduce DA accumulation into renal cells and decrease its endogenous content and availability. This would prevent D1 receptor recruitment and stimulation, while diminishing DA inhibition of Na(+),K(+)-ATPase activity and stimulating sodium reabsorption.