Sodium cyanate-induced ocular lesions in the beagle.

Ocular lesions secondary to sodium cyanate administration in the beagle are described. Fifteen dogs were given sodium cyanate at doses of 30 to 170 mg/kg/day, 5 days per week. Fourteen developed cataracts which were generally posterior and subcapsular. Five animals developed corneal lesions. Control beagles and cyanate-treated rats and monkeys did not develop lesions. The one drug-treated beagle without ocular lesions received a maximum dose of 30 mg/kg/day of sodium cyanate for 19 months and achieved a mean carbamylatin of 0.39 residue of cyanate per mol of hemoglobin. Animals developing cataracts received a maximum dose of 119+/-23 mg/kg/day for 28+/-10 months and achieved a mean carbamylation of 0.69+/-0.13 residue/mol. Animals developing corneal lesions received a maximum dose of 113+/-22 mg/kg/day for 36+/-7 months and achieved a mean carbamylation of 0.78+/-0.09 residue/mol. Younger animals appeared more susceptible to the cataractogenic effects of the drug than older ones. Lens intracellular sodium was increased by 100% in the cataractous lenses while potassium was significantly decreased in the lenses with the greatest opacity. Extracellular space was increased in the cataractous lenses by 61%. Reduced glutathione levels were decreased by 34% and lactate leakage into the medium was increased by 12%. Rubidium-86 uptake was increased by 26% in the cataractous lenses, probably reflecting an inadequate compensatory response to increased passive fluxes of cations resulting from a structural or enzymatic lesion.