| Abstract: | Fragments of thyroid from rats fed Purina +0.1% propylthiouracil were incubated in vitro and the concentration of cyclic AMP measured. The normal gland showed a 3-fold increase in cyclic AMP with 50 mU thyrotropin per ml or 10(-4) M prostaglandin E1; tissue from rats fed propylthiouracil for 10 days to 6 months responded to prostaglandin E1 but not to thyrotropin. Feeding Purina without propylthiouracil for 1 month after 5 months of goitrogen restored thyrotropin-responsiveness, as did, to a lesser extent, injection of triiodothyronine, 50 mug twice daily for 5 days. |
