Modelling cortical cataractogenesis. IV. Induction by hygromycin B in vivo (swine) and in vitro (rat lens)

The cataractogenic effect of the anthelminthic antibiotic hygromycin B was examined. Histochemical staining and scanning electron microscopy of field samples of cataracts from pigs fed hygromycin B were examined in vitro in isolated rat lenses, in vivo in pigs maintained on several defined dietary regimens.In vivo, field samples showed globular degeneration similar to that which we have previously found for human senile posterior cortical subcapsular cataracts (PCSC), including intensified immunofluorescence for α-, β- and γ-crystallins and actin, and similar morphology by scanning electron microscopy. Four dietary regimens were tested: (1) 66 g/t, continuously, (2) 13·2 g/t, continuously, (3) 13·2 g/t intermittently (8 weeks on, 8 weeks off), the manufacturer's suggested regimen, and (4) control. All but one pig on regimens 1 and 2 had developed cataracts with associated globular degeneration when the experiment was terminated after 14 months, but no pigs on regimens 3 and 4 had cataracts.In vitro, in rat lenses incubated in M199 cortical lenticular opacities (cataracts) with associated globular degeneration were found at concentrations of hygromycin B as low as 10^?10m; vitamin E seemed to offer some protection, in that no cataracts were found at 10^?10m-hygromycin if vitamin E (2·4 μm) was also present.The possibility exists that this drug may provide another system for modelling human senile PCSC, as well as a potential cataractogenic agent for human population.