Kinetic analysis of the cerebral @entity908 kinase reaction under XXXX and hypoglycaemic conditions in vitro. A 31P-n.m.r. study.

@entity1734 @entity908 @entity26 @entity840 @entity519 @entity1391 @entity413 @entity4095 @entity855
1. The tissue concentration of @entity1734 (PCr) and the pseudo-first-order rate constant of @entity908 kinase (kf) were monitored in superfused @entity840 brain slices in vitro by using 31P-n.m.r. techniques. 2. Superfusion of slices in low @entity26 partial pressure ( @entity4095 approx. 16 kPa) decreased tissue PCr concentrations by 48% but @entity855 concentrations were unchanged. Regression analysis revealed a significant negative correlation between the PCr concentration in @entity519 tissue and the increase in the rate constant, kf. Nevertheless the forward flux through the enzyme (Jf = kf.[PCr]) declined under these conditions. 3. Lowering the @entity413 concentration to 0.2 or 0.1 mM decreased PCr concentrations by 29% and 48% respectively; here @entity855 concentrations as well as PCr concentrations also decreased. Only in the presence of the lower @entity413 concentration (0.1 mM) was kf increased. However, unlike the situation in @entity519 tissue, Jf was maintained at control rates. 4. In spectra obtained in the presence of low @entity26 or low @entity413 concentrations, a resonance attributable to tissue inorganic @entity1391 became dectectable. This observation is discussed in terms of known changes in tissue @entity1391 concentrations and possible alterations in cytoplasmic pH.
