Role of intrarenal dopamine on renal phosphate regulation

Abstract

Dopamine excretion primarily reflects the tubular synthesis of dopamine. Renal dopamine synthesis occurs primarily in the proximal convoluted and straight tubules. Recent studies suggest that increased phosphate intake increases tubular dopamine synthesis. The infusion of dopamine is phosphaturic and enhances the phosphaturic effect of PTH in diverse conditions of phosphate conservation such as phosphate deprivation or acute respiratory alkalosis. Exogenous dopamine specifically inhibits phosphate transport as illustrated by studies of isolated renal brush border membranes. Inhibition of endogenous dopamine synthesis in normal rats with carbidopa has been demonstrated to increase phosphate reabsorption. Dopamine has been suggested to modulate the effect of atrial natriuretic peptide on phosphate excretion in normal rats and in rats with a remnant kidney. The enhanced phosphate excretion in rats with a remnant kidney is associated with increased dopamine synthesis per nephron. Studies performed in the opossum kidney cells which are analogous to proximal tubule cells indicate that these cells synthesize dopamine, increase cAMP levels and decrease phosphate transport by the same cells suggesting an autocrine/paracrine role for dopamine on phosphate transport by proximal tubules.