STUDIES IN THE HISTOCHEMISTRY OF PLASMALOGENS: I. THE EFFECT OF FORMALIN AND ACROLEIN FIXATION ON THE PLASMALOGENS OF ADRENAL AND BRAIN

Formalin containing fixatives were found to cause a rapid drop in extractable plasmalogens of steer adrenal cortex and medulla and rat brain to 50-60% of the initial value in 4-6 hours. This rapid destructive reaction was followed by a slow decrease so that for several days the plasmalogen levels remained relatively constant. An acrolein containing fixative, although not evaluated with adrenal, showed similar behavior with rat brain. Control experiments show the fixative aldehyde is solely responsible for this plasmalogen loss. This decrease is not paralleled by a similar decrease in extractable total lipid or total phospholipid. It is believed that this decrease represents an actual destruction of the enol-ether bond by chemical reaction with the fixative aldehyde. Although the nature of this reaction is unknown, model experiments show cephalin plasmalogen to be much more labile than choline plasmalogens to formaldehyde, although all the cephalin plasmalogens are not destroyed during the fast reaction in tissue. These experiments also show that steer adrenal cortex and medulla have the same plasmalogen content and that the plasmalogen in either part of the gland responds the same to fixation, even though plasmal staining would indicate that the medulla is richer in plasmalogen. After a period of fixation sufficient to render the plasmal reaction negative in both adrenal cortex and medulla and in rat brain there is still at least 35-50% of the initial plasmalogen present. The intensity of the plasmal stain appears to parallel the concentration of the fixative labile plasmalogen. In these particular tissues there was no suggestion of an increase in free aldehyde over plasmalogen until the tenth day of fixation.