Short-term changes in the 3,5,3′-tri-iodothyronine nuclear receptor-binding capacity of porcine skeletal muscle following food intake

The time-course of changes in the nuclear 3,5,3'-tri-iodothyronine (T3) receptor-binding capacity (Bmax) of longissimus dorsi muscle has been investigated in cold-acclimated young pigs after a single large meal. Measurement of Bmax values 4, 8, 12 and 24 h after feeding indicated a decline in receptor numbers after food intake with the lowest values occurring at 8 h. The receptor numbers then increased significantly, with the values at 12 h being more than 50% higher than those obtained at 8 h. The Bmax values reached their highest level 24 h after feeding. No significant changes in the dissociation constant were observed. Possible reasons for the changes in T3 receptor numbers are discussed and it is suggested that the increase in T3 receptor numbers 12-24 h after feeding may play a role in enhancing the thermogenic capacity of the tissues in response to food.