[Ultrastructural changes in hepatocytes of mice treated with morphine]

In a study of the ultrastructure of hepatocytes in mice treated with morphine a statistically significant increase in the volume density and surface density of smooth endoplasmic reticulum (SER) was observed. Morphometric measurements using the method described by Weibel (2,3) were employed to calculate volume density of smooth and rough endoplasmic reticulum mitochondria, and surface density of rough and smooth endoplasmic reticulum membranes and of the mitochondrial envelope and cristae. Statistical analysis using the t test of Student was carried out for all parameters. Both surface density and volume density of SER in mice treated with morphine increased significantly when compared to mice of control group (P less than 0.05 for surface density of smooth endoplasmic reticulum and P less than 0.01 for volume density of smooth endoplasmic reticulum). These ultrastructural changes after administration of morphine and related opiates are not accompanied by an increase of drug metabolizing enzymes and the huge tolerance observed in mice can be a phenomenon of adaptation at the receptor site (4).