Effect of oestradiol 3-benzoate on the concentrations of retinal and lipids in cod plasma.

1. Determinations of retinal, total lipid and lipid phosphorus were made on 10ml. samples of cod plasma. 2. Immature control fish, injected with 0.2ml. of carrier oil/kg. wt., had 0.73+/-0.12mug. of retinal/100ml. of plasma, and maturing male fish had similar concentrations. Maturing female fish had about 10mug. of retinal/100ml. of plasma. 3. Immature male or female cod given single intramuscular injections of 1mg. of oestradiol-17beta 3-benzoate in 0.2ml. of oil/kg. wt. had 8.54+/-0.59 mug. of retinal/100ml. of plasma after 5 days and about 25mug./100ml. of plasma after 10 days. 4. Oestradiol injections had little effect on the concentration of plasma phospholipids, and no effect on lipids other than phospholipids. 5. For all 116 fish examined, regardless of sex or treatment, the concentration of plasma phospholipid was significantly correlated with that of lipids other than phospholipids (r=0.727), and phospholipids formed 50.4% of the total lipids in cod plasma. 6. Alcohol dehydrogenase was purified from cod liver and shown to oxidize retinol to retinal. It was completely inhibited by 0.1mm-oestradiol. Alternative modes of action of oestradiol are discussed.