31P NMR saturation transfer measurements of the steady state rates of creatine kinase and ATP synthetase in the rat brain

摘要: There are two theories concerning the function of phosphocreatine (PCr) in cellular energy metabolism. In one PCr is seen as a reservoir, functioning to maintain constant cytoplasmic ATP concentrations. The alternate theory postulates that acts an shuttle between site production mitochondria and utilization cytoplasm (reviews [ 1,2]). Both require exchange flux creatine kinase (CPK) reaction be considerably greater than rate hydrolysis. This necessary order stabilize concentrations during transitions workload, or periods when synthesis impaired, such ischaemia. Calculations phosphorylation potential [3] measurements intracellular pH [4] have been based on assumption CPK near equilibrium. It now possible test this vivo using technique 31P NMR saturation transfer; through was 5 times steady state turnover Langendorff perfused rat heart 151. total extractable activities brain similar; 500 pmol . g-’ min-’ [6] 200 [7], measured at 25’C. mitochondrial form enzyme accounts for 30-40% activity [l] 5% [7]. However, both organs very similar per gram protein basis [8]. Despite these similarities, metabolic response decrease efficiency transduction,