Comparative studies on fresh and postmortem isolated synaptosomes: ATPase activities and ouabain binding.

In earlier studies we have established that rat cortical synaptosomes isolated after a 2-h postmortem storage period showed functional performance and morphological characteristics similar to those isolated immediately after decapitation. The present paper is an account of further functional studies involving the activity of Na-K- and Mg-dependent ATPase and the binding of ouabain in postmortem synaptosomes. These functions were found to survive without major alteration even in the 6-h postmortem fractions. On the other hand the 6-h postmortem fractions showed a very slow oxygen consumption unaffected by DNP and veratrine. In both control and postmortem synaptosomes the actual activity of Na-K-ATPase as calculated from the ouabain-sensitive component of oxygen consumption was consistently less than the potential activity of the enzyme revealed if determination was carried out on the basis of phosphate splitting.