Uptake of Benzpyrene by a Chromosomal Phospholipid

Abstract

THE uptake of 3,4-benzpyrene by cells has been of interest to many workers, particularly in view of the carcinogenic properties of this substance. Moreover, it is a fluorescent compound and has been used as a fluorochrome for lipids into which it will dissolve from a hydrotropic solution ; caffeine is usually used for dispersing it finely in water, since alone benzpyrene appears to be almost completely hydrophobic. Berg¹ has used this method in a detailed and extensive study of the distribution of lipids in a wide range of normal and cancerous animal cells and in the root tips of Allium cepa. In order that the lipids should not be affected by his preparatory procedures, he fixed the tissues in formalin which had been stored over powdered chalk ; chalk seems to have the same effect as calcium chloride, which is frequently added with the intention of maintaining a high concentration of calcium ions to immobilize lipids². This method of fixation seems to be much favoured by histologists. The tissue was sectioned with a freezing microtome, and the sections were then stained with benzpyrene. After a very careful investigation, Berg was forced to conclude that in animal and plant nuclei lipids are not present except in the nuclear membrane, and that biochemical demonstrations of these compounds in extracted nuclei were due to contamination by the cytoplasm. Indeed, he found that the nucleus was the one region in cells that never showed uptake of benzpyrene.