Some properties of myeloid bodies induced in rat liver by an antidepressant drug (maprotiline).

The repeated administration of the antidepressant maprotiline to adult rats caused the formation of myeloid bodies in the liver. In situ and in the cell-free state they were shown by acid phosphatase cytochemistry to represent lysosomes. When cytoplasmic extracts of the livers of control and treated animals were subjected to velocity-centrifugation in shallow sucrose gradients, it was found that after drug treatment the peak activities of a series of acid hydrolases were (reversibly) displaced to lower sucrose densities. This behaviour was most likely related to the accumulation of phospholipid-rich material within the myeloid bodies. The subcellular distribution, the level in mitochondria-rich fractions, and some kinetic parameters of the various acid hydrolase activities were not appreciably altered by the medication. The diminished structure-linked latency of a number of acid hydrolases, the greater susceptibility to the influence of Triton X-100 and to a hypoosmotic environment, and the occurrence of structurally damaged particles indicated that the myeloid bodies are more fragile than the lysosomes of control livers.