Ultrastructural studies in 4-aminopyrazolopyrimidine (4-APP)-induced fatty liver.

Ultrastructural alterations of 4-aminopyrazolopyrimidine (4-APP)-induced fatty liver were studied. Light microscopically, liver sections after 3 to 5 days of 4-APP administration demonstrated more extensive fatty changes and highly osmiophilic lipid droplets were mainly observed in the portal zones of the lobules. The most striking ultrastructural alterations were seen in the Golgi complexes and rough endoplasmic reticulum. Golgi complexes were markedly dilated and osmiophilic vesicles were noted near the Golgi complexes. In the rough endoplasmic reticulum, dilatation of cisternae, loss of the parallel arrangement and dilated vesicles, most of which contained diminished numbers of ribosomes, were also seen. In addition, degranulation of rough endoplasmic reticulum was observed. However, no remarkable changes were noted in the mitochondria. Based on these findings, the functional state of the organellae concerned was discussed.