The effect of light stimulation on phospholipids of calf rod outer segments

Abstract

To determine whether light has an effect on the lipids of calf rod outer segment membranes, total phospholipids, alkenyl phospholipids and phospholipid fatty acids were analysed. Ethanolamine phosphoglycerides, choline phosphoglycerides and serine phosphoglycerides were the major phospholipids of calf rod outer segments. They accounted for 43, 37 and 14% of total lipid phosphorus respectively. As in the whole retina, alkenyl phospholipids were found, but in lower amounts. The choline plasmalogens accounted for 3% of total choline phosphoglycerides, and ethanolamine plasmalogens 7% of total ethanolamine phosphoglycerides. The unsaturated fatty acids made up 50% of total fatty acids. The major fatty acids of the rod outer segment phospholipids were docosahexaenoate (41%), palmitate (13%) and stearate (23%). No significant differences were observed between the outer segments kept in the dark or illuminated. This result could not exclude a more specific action of light on certain polyunsaturated fatty acids, possibly on docosahexaenoate which is a major component of the rod outer segments.