31P-saturation-transfer nuclear-magnetic-resonance measurements of XXXX turnover in @entity840 brain slices.

@entity1734 @entity908 @entity840 @entity35 @entity413 @entity855
The technique of 31P saturation-transfer n.m.r. was used to determine the forward and the reverse rate constants of @entity908 phosphotransferase in superfused @entity840 cerebral tissues in vitro. The calculated forward rate constant of 0.22 +/- 0.03s-1 compared well with a previously reported value for @entity35 brain in vivo [Shoubridge, Briggs _ Radda (1982) FEBS Lett. 140, 288-292]. The reverse rate constant was found to be 0.55 +/- 0.10s-1. 3. By using concentrations of @entity855 and @entity1734 estimated previously for this superfused preparation [Cox, Morris, Feeney _ Bachelard (1983) Biochem. J. 212, 365-370], forward and reverse flux rates were calculated to be 0.68 and 0.72 mumol X s-1 X g-1 respectively. The concordance of forward and reverse fluxes contrasts with the situation observed in vitro in other tissues, and suggests that the @entity908 phosphotransferase reaction is at equilibrium under the conditions used here. 4. Lowering the concentration of @entity413 in the superfusing medium from 10mM to 0.5mM had no significant effect on @entity1734 concentration or on the forward ( @entity855 -generating) flux through @entity908 phosphotransferase. The results indicate that a normal @entity1734 content in the presence of lowered @entity413 availability is reflected by an unchanged turnover rate.
