title: Increase in the ADP/ATP exchange in rat liver mitochondria irradiated in vitro by helium-neon laser.
abstract: To gain some insight into the mechanism of cell photostimulation by laser light, measurements were made of the rate of ADP/ATP exchange in mitochondria irradiated with the low power continuous wave Helium Neon laser (energy dose 5 Joules/cm2). To do this a method has been developed to continuously monitor ATP efflux from phosphorylating mitochondria caused by externally added ADP, by photometrically following the NADP+ reduction which occurs in the presence of glucose, hexokinase, glucose-6-phosphate dehydrogenase and effluxed ATP. The NADP+ reduction rate shows hyperbolic dependence on ADP concentration (Km and Vmax values 8.5 +/- 0.87 microM and 20.7 +/- 0.49 nmoles NADP+ reduced/min x mg mitochondrial protein, respectively), and proves to measure the activity of the ADP/ATP translocator as shown by inhibition experiments using atracyloside, powerful inhibitor of this carrier. Irradiation was found to enhance the rate of ADP/ATP antiport, with externally added ADP ranging between 5 and 100 microM. As a result of experiments carried out with mitochondria loaded with either ATP or ADP, the increase in the activity of the ADP/ATP translocator is here proposed to depend on the increase in the electrochemical proton gradient which occurs owing to irradiation of mitochondria.
authors.affiliation: Dipartimento di Biochimica e Biologia Molecolare, Universitá di Bari, Italy.
authors.forename: S
authors.initials: S
authors.lastname: Passarella
authors.forename: A
authors.initials: A
authors.lastname: Ostuni
authors.forename: A
authors.initials: A
authors.lastname: Atlante
authors.forename: E
authors.initials: E
authors.lastname: Quagliariello
mesh_terms: D000244:Adenosine Diphosphate / Q000378:metabolism* / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D001278:Atractyloside / Q000494:pharmacology; D004563:Electrochemistry; D005947:Glucose / Q000378:metabolism; D005954:Glucosephosphate Dehydrogenase / Q000378:metabolism; D006593:Hexokinase / Q000378:metabolism; D007700:Kinetics; D007834:Lasers; D008930:Mitochondria, Liver / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects*; D009249:NADP / Q000378:metabolism; D009840:Oligomycins / Q000494:pharmacology; D010084:Oxidation-Reduction; D010766:Phosphorylation; D051381:Rats; D013053:Spectrophotometry
chemical_list: D009840:Oligomycins; D001278:Atractyloside; D009249:NADP; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D005954:Glucosephosphate Dehydrogenase; D006593:Hexokinase; D005947:Glucose