FIXATION OF HUMAN DETRUSOR SMOOTH-MUSCLE CELLS - ROLE OF OSMOLARITY AND MAGNESIUM-IONS ON THE ULTRASTRUCTURAL MORPHOLOGY

Magnesium ions added to fixatives for processing to Transmission Elect ron Microscopy (TEM) have been claimed to cause relaxation of detrusor smooth muscle cells [1]. This should facilitate the morphologic evalu ation of the tissue. However, magnesium ions are osmotically active an d their addition may cause the fixative to become hypertonic to the ti ssue. To ascertain whether the presence of magnesium ions causes signi ficant changes compared to those found where the osmolarity is raised without the presence of magnesium, human detrusor specimens were fixed in glutaraldehyde to which increasing amounts of MgCl2 or NaCl were a dded in different concentrations. With the addition of increasing amou nts of MgCl2 and NaCl, the osmolarity of the fixative increased, causi ng significant changes in the morphology and morphometry of the tissue . The intercellular distances increased, the cells shrank and the shap e of the cells changed from smooth and rounded to spiky and angulated. With regard to its muscle-relaxing effect, it was not possible to dis tinguish the specimens fixed in magnesium-containing fixatives from th ose without. In this study it was not possible to prove any relaxing e ffect of magnesium ions added to the fixative. On the contrary the mag nesium ions caused an increase in the osmolarity, with significant cha nges in both the morphometry and the morphology of the human detrusor smooth muscle cells.