1. Concomitant Decrease of the Effects of Thyroxin on TRH-Induced TSH Release, and of the Pituitary Content of Triiodothyronine in Animals on Propylthiouracil112
- Author
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Juan Bernal, G. Morreale de Escobar, Mónica García, and F. Escobar Del Rey
- Subjects
endocrine system ,medicine.medical_specialty ,Triiodothyronine ,Chemistry ,medicine.medical_treatment ,Thiouracil ,chemistry.chemical_compound ,Chromatographic separation ,Endocrinology ,Concomitant ,Internal medicine ,medicine ,Once daily ,Saline ,hormones, hormone substitutes, and hormone antagonists - Abstract
To assess the role of T3 derived from T4 in the regulation of TSH release by T4, we have studied the effects of propyl-2-thiouracil (PTU) on a) the activity of T4 as inhibitor of TRH-induced TSH release and b) on the pituitary concentration of T3 derived from T4. Rats were thyroidectomized and injected ip once daily with 1.75 μg/100 g body wt T4 (or 125I-labeled T4) for 2 weeks. Half of the animals received saline (C rats), while the remainder received 2 mg of PTU ip just after the last two T4 doses. 7–8 hr later blood samples were obtained at 0, 5 and 10 min after 100 ng TRH iv. When labeled T4 was used, rats were perfused at the end of the TRH-stimulation test and the pituitaries were collected for chromatographic separation of the labeled iodine-containing compounds derived from T4. The TRH-induced increase in plasma TSH was greater for PTU than for C rats. The amount of T3 derived from T4 in the pituitaries of the PTU-treated rats was smaller than that found for the C animals, and the amount of T4 was...
- Published
- 1974
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