title: Effect of renal interstitial infusion of L-dopa on sodium and phosphate excretions.
abstract: It has been hypothesized that dopamine synthesized by the proximal tubule can act as a paracrine substance that regulates reabsorption by the proximal tubule. The present study was performed to study the effects of the stimulation of endogenous synthesis of dopamine by infusion of L-DOPA directly into the renal interstitium on sodium and phosphate excretions and to determine the roles of D1 and D2 receptors in the response. The infusion of L-DOPA (50 microg/kg/min) into the renal interstitium through an implanted matrix significantly increased the fractional excretion of sodium (FENa) from 1.0%+/-0.2% to 3.1%+/-0.6% and the fractional excretion of phosphate (FEPi) from 23%+/-3% to 36%+/-3%, P < .05, n = 10. The infusion of D1 receptor antagonist SCH23390 or SKF83566 (5 microg/kg/min) into the renal interstitium blocked the natriuretic (FENa 1.5%+/-0.2% to 1.9%+/-0.4%) and phosphaturic (FEPi 41%+/-3% to 41%+/-4%) effects of L-DOPA infusion. The infusion of the D2 receptor antagonist sulpiride at a rate of 4 microg/kg/min into the renal interstitium also attenuated the natriuretic (FENa 1.3%+/-0.3% to 1.6%+/-0.5%) and phosphaturic effects of L-DOPA infusion (FEPi 36%+/-5% to 39%+/-5%). We conclude that the renal interstitial infusion of L-DOPA increases sodium and phosphate excretions and that these responses are mediated by D1 and D2 receptors.
authors.affiliation: Department of Internal Medicine, Mayo Clinic and Foundation, Rochester, Minnesota 55905, USA.
authors.forename: M M
authors.initials: MM
authors.lastname: LeClaire
authors.forename: T J
authors.initials: TJ
authors.lastname: Berndt
authors.forename: F G
authors.initials: FG
authors.lastname: Knox
mesh_terms: D015647:2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D001552:Benzazepines / Q000494:pharmacology; D004298:Dopamine / Q000096:biosynthesis; D015259:Dopamine Agents / Q000494:pharmacology*; D018492:Dopamine Antagonists / Q000494:pharmacology; D065127:Dopamine D2 Receptor Antagonists; D007263:Infusions, Parenteral; D007687:Kidney Tubules, Proximal / Q000187:drug effects* / Q000378:metabolism; D007980:Levodopa / Q000494:pharmacology*; D008297:Male; D009318:Natriuresis / Q000187:drug effects; D010710:Phosphates / Q000652:urine*; D051381:Rats; D017207:Rats, Sprague-Dawley; D017447:Receptors, Dopamine D1 / Q000037:antagonists & inhibitors / Q000378:metabolism; D017448:Receptors, Dopamine D2 / Q000378:metabolism; D012964:Sodium / Q000652:urine*; D013469:Sulpiride / Q000494:pharmacology
chemical_list: D015647:2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine; D001552:Benzazepines; D004298:Dopamine; D015259:Dopamine Agents; D018492:Dopamine Antagonists; D065127:Dopamine D2 Receptor Antagonists; D007980:Levodopa; D010710:Phosphates; D017447:Receptors, Dopamine D1; D017448:Receptors, Dopamine D2; D012964:Sodium; D013469:Sulpiride; C044846:SKF83566