[Show abstract][Hide abstract] ABSTRACT: When pharmacological or basic neurochemical systematic characterization of mitochondrial enzymatic systems correlated to energy transduction processes is attempted, studies must be based on subcellular fractions with a high degree of purity from specific brain areas and from individual animals. Distinct populations of mitochondria heterogenous with respect to biochemical enzyme characteristics from rat brain hippocampus are described. Two mitochondrial populations were derived from synaptosomes by lysis and a third consists of free non-synaptic mitochondria. The maximum rate of some cerebral enzyme activities which are part of energy transduction (citrate synthase, malate dehydrogenase; total NADH-cytochrome c reductase, cytochrome oxidase) and amino acid metabolism (glutamate dehydrogenase) were tested on these mitochondrial populations of 8- and 16-week-old rats. A comprehensive analysis of the data suggests that extensive but highly diversified catalytic expressions of the enzymes studied occur in the hippocampus. This is true even when a short period of the rat life span is studied. Hence the varying pattern of evolution of the differing cerebral mitochondria, probably a consequence of different metabolic functions, should be taken into account in any pharmacological study on these systems.
No preview · Article · Oct 1989 · Mechanisms of Ageing and Development
[Show abstract][Hide abstract] ABSTRACT: 1. In literature two interesting methods are described to obtain from whole pooled brains or areas three types of mitochondria, namely, those of perikaryal origin and those contained in synaptosomes. 2. However, for many types of studies, such "preparative" preparations are not useful; for example, in pharmacological studies only data from a single n number of animals may be of statistical usefulness and may be correctly analyzed by statistical tests. 3. Thus a method is described by which it was possible to characterize by enzyme activities three populations from single rat brain hippocampus. 4. During preparative "analytical" procedure, it was noted that the 10% Ficoll gradients previously used in the literature were unable to separate purified mitochondria-free mitochondria. This gradient should be 12% Ficoll for single areas. 5. In addition, when results are compared using the more appropriate omega 2t for calculations of gravity forces to be applied instead of the maximum or average g for different rotors, enzymatic characterization differed considerably among the various mitochondrial populations. 6. The above considerations are also true when different pestle clearances and/or pestle rotations speeds are used during omogenizations; also lysis conditions are essential. 7. Results showed that selected experimental conditions are to be used when subcellular fractions are to be analyzed biochemically.
No preview · Article · Jul 1989 · Cellular and Molecular Neurobiology