title: Actions of the creatine analogue beta-guanidinopropionic acid on rat heart mitochondria.
abstract: The action of the creatine analogue beta-guanidinopropionic acid (beta-GPA) was examined in rat heart mitochondria and in isolated cardiomyocytes or fibres which were permeabilized with the non-ionic detergent saponin to determine the kinetics of mitochondrial creatine kinase for beta-GPA. Fibres and myocytes were subjected to increasing [ADP] in the presence and absence of beta-GPA or creatine, whereas isolated mitochondria received a similar protocol with increasing [ATP]. In isolated mitochondria given ATP, there was a stimulation of respiration by creatine, but no significant stimulation of respiration by beta-GPA. Further studies on fibres from control and beta-GPA-fed rats also found that beta-GPA is not utilized by the mitochondria, as evidenced by a lack of beta-GPA-stimulated respiration (Km for ADP = 142 +/- 23 microM) compared with control (Km for ADP from 161 +/- 23 microM), but no significant change in Vmax. Therefore the rat heart mitochondria are not responsive to beta-GPA as compared with creatine. Interestingly, the fibres from beta-GPA-fed rats had no creatine- or beta-GPA-stimulated respiration (Km for ADP = 57.3 +/- 7.2 microM for control, 54.2 +/- 7.2 microM with creatine, and 53.5 +/- 7.8 microM with beta-GPA). The mitochondria prepared from the hearts of rats exposed for 10 weeks to 1% beta-GPA in their diet had a significant decrease in Vmax. and a significant decrease in Km for ADP. Thus the hearts from beta-GPA-fed animals may be pathologic, due to a disruption of the creatine kinase energy circuit.
authors.affiliation: Department of Biochemistry, University of Oxford, U.K.
authors.forename: J F
authors.initials: JF
authors.lastname: Clark
authors.forename: Z
authors.initials: Z
authors.lastname: Khuchua
authors.forename: A V
authors.initials: AV
authors.lastname: Kuznetsov
authors.forename: E
authors.initials: E
authors.lastname: Vassil'eva
authors.forename: E
authors.initials: E
authors.lastname: Boehm
authors.forename: G K
authors.initials: GK
authors.lastname: Radda
authors.forename: V
authors.initials: V
authors.lastname: Saks
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D003401:Creatine / Q000031:analogs & derivatives*; D003402:Creatine Kinase / Q000378:metabolism*; D006146:Guanidines / Q000494:pharmacology*; D066298:In Vitro Techniques; D008929:Mitochondria, Heart / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D009206:Myocardium / Q000378:metabolism; D010085:Oxidative Phosphorylation; D010100:Oxygen / Q000378:metabolism; D011422:Propionates / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar
chemical_list: D006146:Guanidines; D011422:Propionates; D000255:Adenosine Triphosphate; D003402:Creatine Kinase; D003401:Creatine; D010100:Oxygen; C005775:guanidinopropionic acid