3'-Azido-3'-deoxythmidine uptake into isolated rat liver mitochondria and impairment of ADP/ATP translocator.
To gain some insight into the mechanism by which 3'-azido-3'-deoxythymidine (AZT) impairs mitochondrial metabolism, [14C]AZT uptake by rat liver mitochondria (RLM) in vitro was investigated. AZT accumulated in mitochondria in a time-dependent manner and entered the mitochondrial matrix. The rate of AZT uptake into mitochondria showed a hyperbolic dependence on the drug concentration and was inhibited by mersalyl, a thiol reagent that cannot enter mitochondria, thus showing that a membrane protein is involved in AZT transport. Investigation into the capability of AZT to affect certain mitochondrial carriers demonstrated that AZT was able to impair the ADP/ATP translocator, but had no effect on Pi, dicarboxylate, tricarboxylate, or oxodicarboxylate carriers. AZT inhibited ADP/ATP antiport in either mitochondria or mitoplasts in a competitive manner with different sensitivity (Ki values were 18.3 +/- 2.9 and 70.2 +/- 5.8 microM, respectively). Consistent with this were isotopic measurements showing that AZT accumulates in the intermembrane space. AZT does not use ADP/ATP carrier to enter mitochondria, as shown by the failure of both carboxyatractyloside (CAT) to inhibit AZT transport into mitochondria and AZT to induce ATP efflux from ATP-loaded mitochondria. ADP/ATP translocator impairment by AZT as one of the biochemical processes responsible for the ATP deficiency syndrome is discussed.
Barile
M
M
Dipartimento di Biochimica e Biologia Molecolare, Università di Bari, Centro di Studio sui Mitocondri e Metabolismo Energetico, Italy.
Valenti
D
D
Passarella
S
S
Quagliariello
E
E
D000818:Animals; D002250:Carbon Radioisotopes; D002851:Chromatography, High Pressure Liquid; D004305:Dose-Response Relationship, Drug; D007425:Intracellular Membranes / Q000378:metabolism; D008297:Male; D008930:Mitochondria, Liver / Q000378:metabolism*; D000226:Mitochondrial ADP, ATP Translocases / Q000037:antagonists & inhibitors*; D051381:Rats; D017208:Rats, Wistar; D015215:Zidovudine / Q000378:metabolism* / Q000494:pharmacology
D002250:Carbon Radioisotopes; D015215:Zidovudine; D000226:Mitochondrial ADP, ATP Translocases