The inactivation of synthetic [ 3H]thyrotrophin releasing hormone (TRH) by plasma was studied in rats treated with propylthiouracil (PTU) alone or with PTU and thyroxine. 48 h after the onset of treatment with thyroxine, the capacity of rat plasma to inactivate [ 3H]TRH was significantly increased. The percentage of deamidation of TRH to TRH free acid was increased 2 fold after 4 days of administration of thyroid hormone. The inactivation of TRH by plasma from hypothyroid patients was compared to that obtained from hyperthyroid patients. Extraction of human plasma incubated with [ 3H]TRH, followed by thin layer electrophoresis, showed that transformation of [ 3H]TRH into TRH free acid was 44% higher in plasma from hyperthyroid than from hypothyroid patients (P<0.05). These data suggest that the inactivation process of TRH by blood proteins could be an important factor in the regulation of the hypothalamo hypophyseal thyroid axis in rat and man.
|Number of pages||8|
|State||Published - Dec 1 1976|
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