Changes in plasma concentrations of thyroxine binding prealbumin and retinol binding protein in Japanese quail after hatching.

1. Male and female Japanese quail (Coturnix coturnix japonica) were reared under short daily photo-periods (8 h light-16 h dark) to inhibit sexual development with free access to food and water. Blood was sampled at frequent intervals for 13 weeks from hatching in order to monitor the developmental changes in plasma concentrations of the two proteins which are important in the transport of retinol, retinol-binding protein (RBP) and thyroxine-binding prealbumin (TBPA). 2. Measurements of body-weight, blood packed cell volume and plasma total protein concentration showed that the birds had a normal pattern of growth and haematological development. Plasma concentrations of TBPA, total immunoreactive RBP (IRBP) and holoRBP were 220, 60 and 45 micrograms/ml respectively in 1-d-old quail and rose to 430, 165 and 140 micrograms/ml at 14 d of age, which was 10 d after the corresponding change in total protein. Neither RBP nor TBPA concentrations were significantly different between the sexes during the 13 weeks, but there were minor fluctuations in concentration within relatively narrow limits.