Ultrastructural studies on autolysosomes in rat hepatocytes after leupeptin treatment.

We have studied the morphological alterations of the lysosomal compartment in rat hepatocytes following intraperitoneal administration of leupeptin, using electron microscopy and cytochemical techniques. At 30 min after the injection, autophagic vacuoles (autophagosomes and autolysosomes), containing cytoplasmic organelles, increased in number in the vicinity of bile canaliculi and also near the Golgi apparatus. At 1 h, most of the autophagic vacuoles were autolysosomes, single membrane-limited bodies positive for acid phosphatase activity. Development of the autolysosomes was accompanied by the reciprocal disappearance of pre-existing secondary lysosomes. From 1 to 8 h, the autolysosomes varied to a great extent in both size and shape as a result of coalescence. Segregated organelles within the autolysosomes were gradually degraded into electron-lucent unidentifiable debris. At later, residual bodies were abundant in the cytoplasm, and occasionally, their contents were discharged into the space of Disse. From 9 to 12 h, the autolysosomes decreased in the volume and number and secondary lysosomes of normal shape and size appeared. The autolysosomes seem to persist for long periods because of a retarded degradation of sequestered materials in leupeptin-treated hepatocytes.