Leakage of insulin-degrading activity from rat liver cells in suspension and primary monolayer culture

198 l), probably through increased release of thyrotropin from the pituitary, but thyroid activity later declines as the plasma concentration of gonadal steroid hormones increase and have a feedback affect on the pituitary as well as affecting T, utilization (Jallageas & Assenmacher, 1972). Increasing the photoperiod, however, simultaneously brings about a steady decline in plasma TBPA concentration. The above results, which show a good correlation between this specific carrier and T,, indicate that it has an important function in regulating or limiting the rate of transport of T, from the thyroid to the peripheral tissues in birds.