The rod outer segment phospholipid/opsin ratio of rats maintained in darkness or cyclic light.

Rhodopsin (opsin), lipid, and fatty acids were measured in rod outer segments (ROS's) of rats maintained for at least 2 weeks in continuous darkness or in 12 hours per day cyclic light. Average rhodopsin per eye was 1.8 nmol. for the 5 ft.-c. cyclic light groups compared to 2.4 nmol. for the dark groups of the same age. The phospholipid/opsin ratio was significantly higher after cyclic light maintenance, suggesting that slow adaptive processes control the opsin density of the ROS membranes. Estimates indicate that ROS length also depends on the long-term light environment. ROS lipid and fatty acid composition were not consistently different in dark and light groups.