title: Role of 20-HETE in D1/D2 dopamine receptor synergism resulting in the inhibition of Na+-K+-ATPase activity in the proximal tubule.
abstract: Previous studies propose 20-hydroxyeicosatetraenoic acid (20-HETE), a major arachidonic acid metabolite of cytochrome P-450 (CYP), as a possible mediator of Na(+)-K(+)-ATPase inhibition by dopamine (DA). The aim of this study was to investigate the intracellular mechanisms involved in this effect and to elucidate the DA receptor associated with the 20-HETE pathway in the rat kidney. DA (10(-5) M) inhibited Na(+)-K(+)-ATPase activity in microdissected tubular segments to 59.4 +/- 3.8% of control activity. This response was suppressed by the CYP4A inhibitor 17-octadecynoic acid (10(-6) M), which had no effect per se, thus confirming the participation of CYP arachidonic acid metabolites in DA-induced Na(+)-K(+)-ATPase inhibition. We next examined whether 20-HETE is involved in the signaling pathways triggered by either D(1) or D(2) receptors. Neither fenoldopam nor quinpirole (D(1) and D(2) agonists, respectively, both 10(-5) M) modified Na(+)-K(+)-ATPase activity when tried alone. However, coincubation of a threshold concentration of 20-HETE (10(-9) M) with fenoldopam resulted in a synergistic inhibition of Na(+)-K(+)-ATPase activity (66 +/- 2% of control activity), while 20-HETE plus quinpirole had no effect. Furthermore, 20-HETE (10(-9) M) synergized with forskolin (10(-5) M) and with the diacylglycerol analog 1-oleoyl-2-acetoyl-sn-glycerol (OAG; 10(-11) M; 62.0 +/- 5.3 and 69.9 +/- 2.0% of control activity, respectively), indicating a cooperative role of 20-HETE with the D(1)-triggered pathways. In line with these results, no additive effect was observed when OAG and 20-HETE were combined at concentrations which per se produced maximal inhibition (10(-6) M). These results demonstrate that the inhibition of Na(+)-K(+)-ATPase activity by DA in the proximal tubule may be the result of the synergism between 20-HETE and the D(1) signaling pathway.
authors.affiliation: Centro de Investigaciones Endocrinológicas CONICET, Facultad de Medicina, Universidad de Buenos Aires, Buenos Aires, Argentina.
authors.forename: Carolina
authors.initials: C
authors.lastname: Kirchheimer
authors.forename: Carlos F
authors.initials: CF
authors.lastname: Mendez
authors.forename: Andrea
authors.initials: A
authors.lastname: Acquier
authors.forename: Susana
authors.initials: S
authors.lastname: Nowicki
mesh_terms: D000818:Animals; D005576:Colforsin / Q000494:pharmacology; D004075:Diglycerides / Q000494:pharmacology; D004298:Dopamine / Q000494:pharmacology; D018491:Dopamine Agonists / Q000494:pharmacology; D004357:Drug Synergism; D005231:Fatty Acids, Unsaturated / Q000494:pharmacology; D018818:Fenoldopam / Q000494:pharmacology; D006893:Hydroxyeicosatetraenoic Acids / Q000494:pharmacology / Q000502:physiology*; D007687:Kidney Tubules, Proximal / Q000166:cytology / Q000201:enzymology / Q000378:metabolism*; D008297:Male; D051571:Protein Kinase C-alpha / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D017447:Receptors, Dopamine D1 / Q000378:metabolism / Q000502:physiology*; D017448:Receptors, Dopamine D2 / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors* / Q000378:metabolism; D013347:Subcellular Fractions / Q000201:enzymology; D014018:Tissue Distribution
chemical_list: C520323:1-oleoyl-2-acetoyl-sn-glycerol; D004075:Diglycerides; D018491:Dopamine Agonists; D005231:Fatty Acids, Unsaturated; D006893:Hydroxyeicosatetraenoic Acids; D017447:Receptors, Dopamine D1; D017448:Receptors, Dopamine D2; D005576:Colforsin; C047008:17-octadecynoic acid; C055987:20-hydroxy-5,8,11,14-eicosatetraenoic acid; D051571:Protein Kinase C-alpha; D000254:Sodium-Potassium-Exchanging ATPase; D018818:Fenoldopam; D004298:Dopamine