Retinal in the blood and liver of the fowl in relation to sex and maturity.

1. Concentrations of retinal (vitamin A(1) aldehyde) in the plasma and liver of laying hens, mature cockerels, immature pullets and pullets undergoing sexual maturation have been measured. 2. The plasma of laying hens contained about 8mug. of retinal/100ml., about ten times that found in the plasma of mature cockerels and immature pullets. In laying hens that had received large doses of retinyl palmitate 8-4 weeks previously, the mean concentration of retinal was 18.3mug./100ml. of plasma. 3. The appearance of significant amounts of retinal in the plasma of maturing pullets coincided with hypertrophy of the oviduct, increase in concentration of plasma lipid and onset of egg-laying. 4. Retinal was present in the livers of all types of fowl examined and the concentrations, which ranged from 0.2 to 5.8mug./g. wet wt., were highly correlated (r=0.79) with the concentrations of liver retinyl esters, which ranged from 92 to 1530mug./g. wet wt.