Revista Portuguesa de Nefrologia e Hipertensão 133 RENAL DOPAMINE SYSTEM IN CHRONIC RENAL INSUFFICIENCY Rev Port Nefrol Hipert 2005; 19 (3): 133-141 ABSTRACT In the periphery, physiological dopamine in- creases renal blood flow, decreases renal re- sistance and acts on the kidney tubule to en- hance natriuresis and diuresis. Dopamine receptors can be divided into D 1 -like (D 1 and D 5 ) receptors that stimulate adenylyl cyclase and D 2 -like (D 2 , D 3 and D 4 ) receptors that inhibit adenylyl cyclase. Both the D 1 -like and D 2 -like receptors are expressed in the kidney. Dopamine is synthesized in the epithelial cells of the proxi- mal tubules which are endowed with a high aro- matic L-amino acid decarboxylase (L-AADC) Renal dopamine system in chronic renal insufficiency Manuel Pestana 1 , Benedita Sampaio-Maia 2 1 Unit of Research & Development of Nephrology and 2 Institute of Pharmacology & Therapeutics. Faculty of Medicine, University of Porto. Portugal Editorial Recebido em: 05/11/2004 Aceite em: 12/01/2005 activity. Dopamine of renal origin behaves as an endogenous natriuretic hormone interacting with tubular D 1 -like receptors to inhibit the Na + - K + ATPase and Na + -H + exchanger, as a paracrine/autocrine substance. Dopamine newly synthesized in tubular epithelial cells un- dergoes extensive deamination and methylation by monoamine oxidase and catechol- O - methyltransferase, respectively. During moder- ate sodium surfeit, dopamine of renal origin ac- counts for ~50% of sodium excretion. In experimental and human hypertension a re- duced renal production of dopamine and a D 1 receptor-G protein coupling defect have been reported. Patients suffering from chronic parenchymal diseases with a compromised renal function present a reduced renal dopamine output which correlates well with the degree of