Adrenaline stimulates H2O2 generation in liver via NADPH oxidase.
It is known that adrenaline promotes hydroxyl radical generation in isolated rat hepatocytes. The aim of this work was to investigate a potential role of NADPH oxidase (Nox) isoforms for an oxidative stress signal in response to adrenaline in hepatocytes. Enriched plasma membranes from isolated rat liver cells were prepared for this purpose. These membranes showed catalytic activity of Nox isoforms, probably Nox 2 based on its complete inhibition with specific antibodies. NADPH was oxidized to convert O(2) into superoxide radical, later transformed into H(2)O(2). This enzymatic activity requires previous activation with either 3 mM Mn(2+) or guanosine 5'-0-(3-thiotriphosphate) (GTPgammaS) plus adrenaline. Experimental conditions for activation and catalytic steps were set up: ATP was not required; S(0.5) for NADPH was 44 microM; S(0.5) for FAD was 8 microM; NADH up to 1 mM was not substrate, and diphenyleneiodonium was inhibitory. Activation with GTPgammaS plus adrenaline was dose- and Ca(2+)-dependent and proceeded through alpha(1)-adrenergic receptors (AR), whereas beta-AR stimulation resulted in inhibition of Nox activity. These results lead us to propose H(2)O(2) as additional transduction signal for adrenaline response in hepatic cells.
Díaz-Cruz
Antonio
A
Department of Animal Nutrition and Biochemistry, Faculty of Veterinary Medicine and Zootechnics, National Autonomous University of Mexico (UNAM), Mexico City, Mexico. adc@servidor.unam.mx
Guinzberg
Raquel
R
Guerra
Ruy
R
Vilchis
Magdalena
M
Carrasco
Daniel
D
García-Vázquez
Francisco J
FJ
Piña
Enrique
E
D000322:Adrenergic Agonists / Q000494:pharmacology*; D000818:Animals; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects*; D004837:Epinephrine / Q000494:pharmacology*; D022781:Hepatocytes / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D006861:Hydrogen Peroxide / Q000378:metabolism*; D008110:Liver Extracts / Q000378:metabolism*; D008297:Male; D019255:NADPH Oxidases / Q000378:metabolism*; D016877:Oxidants / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D011941:Receptors, Adrenergic / Q000737:chemistry / Q000378:metabolism
D000322:Adrenergic Agonists; D008110:Liver Extracts; D016877:Oxidants; D011941:Receptors, Adrenergic; D006861:Hydrogen Peroxide; D019255:NADPH Oxidases; D004837:Epinephrine