In this study, we compared hepatic ultrastructure in healthy cats, in cats with severe hepatic lipidosis, and in cats with experimentally induced, chronic, extrahepatic bile duct occlusion. Ultrastructural features unique to the lipidosis syndrome included an apparent reduction in number of peroxisomes and alteration in their morphologic features. The quantity of endoplasmic reticulum, Golgi complexes, and lysosomes was subjectively reduced, and paucity of cytosolic glycogen was observed. Bile canaliculi appeared collapsed because of cytosolic distention with lipid. Mitochondria were reduced in number and were markedly pleomorphic. Cristae assumed a variety of shapes, lengths, and orientations. Ultrastructural features of bile duct occlusion were similar to those described in other species and differed from those in cats with hepatic lipidosis.

An R664X nonsense mutant AE1 is responsible for dominant hereditary spherocytosis in cattle and is degraded by the proteasomal endoplasmic reticulum-associated degradation. The present study demonstrated that R664X AE1 translated in vitro had the trypsin-sensitve site identical to that of the wild-type AE1. The P661S/R664X mutant containing a possible N-glycosylation site at Asnsup(660) showed an increase in size by 3 kDa both in the cell-free translation system and in transfected HEK293 cells. Moreover, steady state levels of R664X and P661S/R664X in HEK293 cells were markedly increased in the presence of a proteasome inhibitior. These findings indicate that the truncated C-terminal region of R664X AE1 has lumenal localization in the endoplasmic reticulum and is not accessible to proteasomal machineries in the cytosol.