The effects of
mirex on growth, histology, and K+ and Na+ concentrations of the fetal lens are examined. Pregnant Long-Evans rats were intubated with 6 mg/kg/day
mirex in
peanut oil on days 8-15 of gestation. Control dams received pure
peanut oil. Fetuses were removed on days 18-21 and rated for extent of lens opacification and degree of
edema.
Lenses were removed, weighed, and assayed for K+ and Na+. Selected eyes were examined histologically.
Cataracts were found in 49.6% of live treated fetuses on day 20, and the incidence and severity of
cataracts were both correlated with the degree of
fetal edema. Lens weights were reduced in treated litters whether or not
cataracts occurred, but the reduction in cataractous
lenses was greater.
Sodium tended to be elevated and K+ reduced in
lenses from treated fetuses, and the K+/Na+ ratio was significantly reduced in all treated groups. Histologically, treated
lenses had swollen fibers on day 18 and areas of apparent cell breakdown by day 20. The swollen lens fibers, reduced K+/Na+ ratios and the correlation with
edema suggest that fetal
cataracts induced by
mirex may be due to lens fiber cell breakdown subsequent to osmotic swelling.