Humans have dopamine D5 receptors(hD5R)with single nucleotide polymorphisms and diminished function.The negative interaction between D5R and AT1R is involved in the regulation of renal sodium transport and pathogenesis of hypertension.We generated hD5F173L cDNA that has a decreased response to D5R agonist-mediated increase in cAMP production and increased production of reactive oxygen species,relative to wild-type hD5R(hD5WT)cDNA expressed in Chinese hamster ovary cells.To investigate the role of hD5F173L in the pathogenesis of salt-sensitive hypertension,we generated transgenic mice overexpressing hD5F173L or hD5WT and fed them normal(0.8%NaCl)or high(4%NaCl)salt diet.On normal salt diet,the blood pressure,and renal NADPH oxidase activity and angiotensin type 1 receptor(AT1R)expression were higher in hD5F173L than hD5WT transgenic mice.After two weeks on high salt diet,the blood pressure and renal NADPH oxidase activity,but not AT1R expression,were increased in hD5F173L but not in hD5WT transgenic mice.Candesartan,an AT1R antagonist,decreased the blood pressure and NADPH oxidase activity in hD5F173L but not in hD5WT transgenic mice.We suggest that the ability of the hD5R to negatively regulate renal NADPH oxidase activity and AT1R function may have important implications in the pathogenesis of salt-sensitive blood pressure.A proper balance between dopamine and the renin-angiotensin systems in the kidney is needed to maintain normal renal sodium excretion and their abnormal interaction leads to sodium retention and ultimately an increase in blood pressure.