Philly mouse: A new model of hereditary cataract

Philly mouse is a new strain of mice derived from the Swiss-Webster strain which develops hereditary cataracts visible to the naked eye ca. 5-6 weeks after birth. Slit lamp examinations of the apparently clear lenses of 15 day mice indicate the presence of faint anterior opacities which progress, involving the suture area, by day 25. By 30 days a nuclear opacity develops which surrounds the nucleus by day 35. At the same time the anterior subcapsular opacity becomes diffuse and pronounced as the cataract becomes obvious to the naked eye. Biochemical studies indicate that an osmotic cataract is formed in the Philly mouse. By ca. 20 days of age there is an increase in lens water along with an alteration in electrolyte levels. Lenticular sodium rapidly increases while potassium levels decrease. Concomitant with cataract formation is an increase in total lenticular calcium and a decrease in lens dry weight, reduced GSH and ATP. In transport studies, no significant difference between the Philly and control lens was seen in the accumulation of AIB. When rubidium was substituted for potassium a decreased accumulation in the Philly lens older than 20 days was correlated with increased rubidium leak-out. This decreased accumulation due to increased leak-out appears to be the key biochemical change that accounts for osmotic cataract formation and it suggests the possibility of a defect in membrane permeability.