Does the pentose cycle play a major role for NADPH supply in the heart?
It was attempted to determine the substrate flux through the pentose cycle in isolated rat hearts which performed pressure-volume work employing 14CO2 production from [1-14C]glucose (Kühn & Scholz (1982) Eur. J. Biochem. 124, 611-617). Even under conditions of increased NADPH requirements (infusion of tert-butylhydroperoxide) and a diminished 14CO2 production from glucose via the citrate cycle (in the presence of oleate as additional substrate) or enhanced activity of glucose-6-phosphate dehydrogenase (pretreatment with isoproterenol), a substrate flux through the pentose cycle was not detectable. The lower limit of detection is 0.01 mumol/(min X g). The increase in 14CO2 production from [1-14C]- and [6-14C]glucose and the acceleration in the washout when tert-butylhydroperoxide was present suggest an increase of substrate flux through the citrate cycle; therefore it is concluded that NADPH required for the removal of peroxides via the glutathione system is derived from the isocitrate dehydrogenase reaction.
D000818:Animals; D005947:Glucose / Q000378:metabolism; D066298:In Vitro Techniques; D007700:Kinetics; D008297:Male; D009206:Myocardium / Q000378:metabolism*; D009249:NADP / Q000378:metabolism*; D010427:Pentose Phosphate Pathway; D010477:Perfusion; D010545:Peroxides / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains
D010545:Peroxides; D009249:NADP; D005947:Glucose