Effect of AY9944 on Lffld metabolism, histogenesis, and ros membrane assembly in developing rat retina

Purpose. AY9944 blocks cholesterol (ΔA⁵) biosynthesis, resulting in excessive tissue accumulation of 7-dehydrocholesterol (Δ^5,7), and has teratogenic effects in utero. We evaluated the effects of AY9944 on retinal sterol biosynthesis, histogenesis, and rod outer segment (ROS) membrane assembly in developing rat retinas. Methods- Pregnant Sprague-Dawley rats (5- to 7-days sperm-positive) in the "treated" group were fed lab chow containing AY9944 (1-2 mg/100 g chow up to Iday prenatal, then 20 mg/100 g thereafter); the "control" group received normal chow. Pups were sacrificed in pairs at intervals up to 8 weeks postnatal; sterol analysis of retina, liver, brain, and serum was performed by HPLC, with correlative histological analysis of retinas. At 4-6 wk., one group each of treated vs. control pups was injected intravttreally with [3H]acetate; 20 h later, retinas were removed, saponified, and the nonsaponifiable lipids (NSLs) were analyzed by radio-HPLC. Another group of each was injected intravitreally with [³H]leucine; 4 days later, eyes were processed for light microscopic autoradiography (LMARG). Results. Although pupsinthe treated group weighed 25-35% less than agematched controls, they were not dysmorphic and did not have cataracts. All tissues in the treated group exhibited marked accumulation of Δ^5,7 and concomhantly reduced Δ⁵ content, relative to controls (which contained little or no Δ^5,7). Δ^5,7 was the predominant radiolabeled retinal NSL constituent in the treated group, whereas Δ⁵ was the major radiolabeled NSL in control retinas. LM of treated vs. control eyes showed no appreciable differences in retinal histology, and LMARG showed no apparent differences in displacement of ROS silver grain "bands." Conclusions. AY9944 can cause marked changes in retina steady-state sterol mass and sterol biosynthesis, without affecting retinal histogenesis or ROS membrane assembly. [Supported by NIH grants EY07361 and EY06045 (SJF), and by Research to Prevent Blindness, Inc.] (None).