Quantitative ultrastructure of the rat liver by immersion and perfusion fixations

Morphometric and qualitative investigations of rat liver with immersion fixation (I) and perfusion fixation (P) have not produced any statistically significant differences in the volume densities and numbers per area of elements of hepatocytes: Vv mitochondria: 0.194 (I), 0.189 (P); peroxisomes 0.011 (I), 0.012 (P); glycogen 0.196 (I), 0.183 (P); agranular endoplasmic reticulum 0.144 (I), 0.183 (P); granular endoplasmic reticulum and groundplasm 0.455 (I), 0.437 (P). The numbers per unit area (micrometers 2) for the mitochondria are 0.492 (I) and 0.496 (P), and for the peroxisomes 0.048 (I) and 0.044 (P), respectively. From the results, the following conclusions can be drawn: -- There are no differences in qualitative and quantitative findings as to the preservation of the hepatocytes by immersion and perfusion fixation. Immersion fixation can be applied as analogous and equivalent methods in routine investigations of human excision and bioptic tissues and also of very large and very small organs. -- Ischemic autolytic alterations of the cells, especially in the mitochondria occur: with immersion fixation in the surface zone and the central zone of the specimen (the intermediate zone is well preserved), with perfusion fixation in different areas. -- Alterations in the sinusoidal wall affect the width of the lumen and the openings of the endothelial cells which show better conditions at optimum pressure and flow rate of the perfusion fluid. -- Pronounced alterations in the endothelial cells, partially the total destruction and detachment are caused by non-optimal pressure and flow rates of the perfusion. They may appear, however, as secondary results caused by the composition of the fluid or circumscribed constrictions of the vascular system of the liver. -- With regard to the transplantology of the liver the studies on the perfusion fixation demonstrate the importance of pressure, flow rate and composition of the perfusion fluid for preserving the tissue, especially the sinusoidal wall.