Prolactin and dopamine 1-like receptor interaction in renal proximal tubular cells.

Prolactin is a natriuretic hormone and acts by inhibiting the activity of renal tubular Na(+)-K(+)-ATPase activity. These effects require an intact renal dopamine system. Here, we have studied by which mechanism prolactin and dopamine interact in Sprague-Dawley rat renal tissue. Na(+)-K(+)-ATPase activity was measured as ouabain-sensitive ATP hydrolysis in microdissected renal proximal tubular segments. Intracellular signaling pathways were studied by a variety of different techniques, including Western blotting using phosphospecific antibodies, immunoprecipitation, and biotinylation assays. We found that dopamine and prolactin regulated Na(+)-K(+)-ATPase activity via similar signaling pathways, including protein kinase A, protein kinase C, and phosphoinositide 3-kinase activation. The cross talk between prolactin and dopamine 1-like receptors was explained by a heterologous recruitment of dopamine 1-like receptors to the plasma membrane in renal proximal tubular cells. Prolactin had no effect on Na(+)-K(+)-ATPase activity in spontaneously hypertensive rats, a rat strain with a blunted response to dopamine. These results further emphasize the central role of the renal dopamine system in the interactive regulation of renal tubular salt balance.