Fig. 9.

Ultrastructural changes caused by azathioprine in canine liver (from nontransplanted animals). A, after 40 days of azathioprine treatment. With light microscopy, there was pallor of centrilobular hepatocytes but no necrosis. This electron micrograph shows that cytoplasm lacks glycogen and the normal amount of rough endoplasmic reticulum, but contains an excess of lipofuscin (L) and lipid (arrow). Bile canaliculi are unaltered; ×2000. B, more severely damaged liver after azathioprine treatment for 40 days. Centrilobular hepatocyte necrosis was evident on light microscopy, similar to that in Figure 8. Two bile canaliculi (arrows) are blocked by inspissated bile. Microvilli in the larger of the canaliculi are scanty and short. Adjoining hepatocytes lack glycogen and normal amount of rough endoplasmic reticulum and contain excess lipofuscin (L). Electron micrograph; ×4000.