A COMPARISON OF THE EFFECTS OF THREE WIDELY USED GLUTARALDEHYDE FIXATIVES ON CELLULAR VOLUME AND STRUCTURE

Abstract

The effects of 3 widely used glutaraldehyde-based fixatives on cellular volume and structure were studied utilizing TEM [transmission electron microscopy], SEM [scanning electron microscopy], time-lapse micrography during the fixation procedure, volumetry and demonstration of the lysosomal enzyme acid phosphatase. The cells used were in vitro cultivated human glia and glioma cells and suspensions of isolated rat liver parenchymal cells. The fixatives compared were the following: 2% glutaraldehyde (GA) in 0.1 M sodium-cacodylate hydrochloride buffer (cac) with 0.1 M sucrose (pH 7.2); total osmolality (T) 510 mOsmol; vehicle osmolality (V) 300 mOsmol, 2% GA in 0.1 M cac (pH 7.2; T = 410 mOsmol; V = 200 mOsmol) and 1.5% GA in 0.067 cac with 0.033 M sucrose (pH 7.2; T = 320 mOsmol; V = 170 mOsmol). The fixative with a vehicle osmolality of 300 mOsmol gave results which were interpreted as ideal while the 2 fixatives with hypotonic vehicles resulted in changes which were easily demonstrated using volumetry, time-lapse micrography, SEM and cytochemistry. The differences observed in the TEM were less obvious and difficult to interpret, the major alterations being changes in the configuration of the ER in the liver cells. Even small variations in the composition of a glutaraldehyde fixative can result in structural changes which do not correspond to the functional morphology of a living cell. Such changes make correct interpretation of micrographs difficult.