Stereologic studies on mitochondrial configuration in different organs of the rat

Summary Mitochondria from different organs of the rat with configurations ultrastructurally resembling those of isolated mitochondria of known respiratory states have been subjected to Stereologic analysis. Mitochondria were examined from mossy fibers of the granular layer of the cerebellar cortex (condensed state), of the pericentral hepatocytes (orthodox state), and of heart muscle and parietal cells of the gastric fundus (transitional state). In order to study the relationship between mitochondrial compartments and the internal membrane a partition coefficient was introduced, which expresses the volume of the matrix (E_mm) and external compartment (E_ocm) respectively per unit surface area of internal mitochondrial membrane. The Stereologic parameters investigated, i.e. surface density of the mitochondrial membranes, volume density of the mitochondrial compartments and membranes, and partition coefficients generally agreed with the visual evaluation of mitochondrial ultrastructure. However, analysis of the coefficient of variation /x × 100% for E_ocm and E_mm has shown significantly greater variability in the mitochondria of the myocardium than in the gastric mitochondria, despite similar ultrastructure. It is suggested that Stereologic methods, like time-lapse cinematography, give a compound picture of configurational variation and of its plasticity.