[Comparison of homologous and heterologous standard curves using TR-FIA for the determination of total T4 in the rat].

A homologous standard curve for rat T4 measurement has been compared to heterologous standard curves, by a time resolved fluoroimmunoassay (TR-FIA). Homologous standard curves have been carried out starting from rat serum in the absence of thyroid hormone by using Samuel's technique. The security criteria (sensitivity, inter and intraassay precision, and accuracy), were measured and compared between the homologous and heterologous test.

Influence of thyroid hormone deficiency on the citrate synthase activity in rat brain regions during early postnatal development.

The developmental pattern of citrate synthase activity has been studied in the liver and several brain areas of hypothyroid rats during the 4 first weeks of life. While citrate synthase activity in the liver showed a rise during the 2 first weeks of life, different patterns of enzyme activity were found in the brain regions of euthyroid animals. Citrate synthase activity increased in the cerebellum, decreased in the cerebral cortex and did not change significantly in the brain stem during the period studied.