Saturable 3,5,3′-triiodo-l-thyronine-binding sites in liver nuclei of rainbow trout (Salmo gairdneri Richardson)

Saturable binding of 3,5,3′-triiodo-l-thyronine (T3) was demonstrated in liver nuclei of rainbow trout using an in vivo isotope displacement method; saturable T3 sites were not found in mitochondrial, microsomal, or cytosol fractions. Equilibrium constants ranged from 0.9 to 1.2 × 108 kg liver/mol T3, indicating an affinity comparable to that of mammals. Binding capacities ranged from 0.43 to 0.62 × 10−12 mol T3/g liver. Approximately 50% of …