Ultrastructural changes in the mouse liver induced by hepatotoxin from the freshwater cyanobacterium Microcystis aeruginosa strain 7820.

The time-course of ultrastructural changes was studied in mouse liver hepatocytes after i.p. injection of lethal (100 micrograms/kg) and sublethal (10 micrograms/kg) doses of the heptapeptide hepatotoxin from Microcystis aeruginosa strain 7820, a freshwater blue-green alga (cyanobacterium). At both dose levels the hepatocytes show progressive intracellular changes over time periods of 10, 20, 30, and 60 min. The changes resulting from a lethal dose were more prominent and rapid compared to those of the sublethal dose. The most common responses to lethal and sublethal doses were vesiculation of rough endoplasmic reticulum, swollen mitochondria and degranulation (partial or total loss of ribosomes from vesicles). These vesicles appear to have formed from the dilated parts of rough endoplasmic reticulum by fragmentation or separation. At the lethal dose an increased amount of whorl shaped rough endoplasmic reticulum along with large membrane-bound vacuoles were observed in the cytoplasm. With the sublethal dose an increase in the amount of small and large cytoplasmic lipid droplets occurred. These ultrastructural changes parallel the pathological events which lead to animal death by hemorrhagic shock.