CYTOCHEMISTRY OF PINEAL LIPIDS IN RAT AND MAN

Lipid cytochemistry studied in 130 rat pineals demonstrates two common types of parenchymal cells which may be involved in an endocrine secretory activity. The first cell type is characterized by its content of abundant lipid droplets, composed primarily of ethanol-soluble carbonyl lipids coated with phospholipid. The second cell type is distinguished by its content of a phospholipid cytoplasmic matrix containing few droplets on vacuoles. This cell type appears to be identical with the cell staining with orange G or phloxine in a modified chrome alum hematoxylin technique described previously. Parenchymal cells containing lipid occur in seven human pineals of diverse ages; and in the older pineals interlobular cells containing lipid occur as well. The lipid in human parenchymal cells differs from that in the type 1 parenchymal cells of the rat by, (1) forming smaller droplets, (2) containing a greater amount of neutral lipid and less carbonyl lipid, and (3) being associated with pigment fomation in adults and older people.