Acute experimental autoimmune encephalomyelitis (EAE) is an inflammatory disease of the central nervous system, mediated by T lymphocytes. Immunization of Lewis rats with myelin antigens suspended in complete Freund’s adjuvant induces EAE. In a previous study on rats we have found that neurointermediate pituitary lobectomy (NIL) decreased both the humoral and cell-mediated immune responses. Here we investigated the effect of NIL on the incidence and severity of EAE and on the function of the hypothalamic-pituitary-adrenal axis in Lewis rats. NIL, hypophysectomized (Hypox) and sham-operated (Sham) rats were immunized s.c. with guinea-pig brain extract suspended in complete Freund’s adjuvant. Untreated rats were used as controls. Water intake, body weight gain, clinical and histopathologic incidence and severity of EAE were evaluated in the operated groups. On killing, plasma adrenocorticotropin and corticosterone levels were measured and adrenals, thymuses and spleens were weighed. Histopathologic lesions were counted in the brain and spinal cord. Water intake and body weight gain were significantly decreased in Sham and Hypox animals with EAE whereas higher intakes persisted in the NIL group. Plasma levels of adrenocorticotropin were within the normal range whereas corticosterone levels increased in Sham and occasionally in NIL animals. Thymus weights were decreased in NIL and Hypox groups. The clinical and histopathologic incidence and severity of EAE were significantly decreased in NIL animals as compared with Sham and Hypox rats. We concluded that NIL affects the cell-mediated immune response and plays a role in the development and progression of EAE in the Lewis rat.

Iodide is a trace element and a key component of thyroid hormones (TH). The availability of this halogen is the rate-limiting step for TH synthesis; therefore, thyroidal iodide uptake and recycling during TH synthesis are of major importance in maintaining an adequate supply. In the rat, the thyroid gland co-expresses a distinctive pair of intrathyroidal deiodinating enzymes: the thyroid iodotyrosine dehalogenase (tDh) and the iodothyronine deiodinase type 1 (ID1). In the present work, we studied the activity of these two dehalogenases in conditions of hypo- and hyperthyroidism as well as during acute and chronic iodide administration in both intact and hypophysectomized (HPX) rats. In order to confirm our observations, we also measured the mRNA levels for both dehalogenases and for the sodium/iodide symporter, the protein responsible for thyroidal iodide uptake. Our results show that triiodothyronine differentially regulates tDh and ID1 enzymatic activities, and that both acute and chronic iodide administration significantly decreases rat tDh and ID1 activities and mRNA levels. Conversely, both enzymatic activities increase when intrathyroidal iodide is pharmacologically depleted in TSH-replaced HPX rats. These results show a regulatory effect by iodide on the intrathyroidal dehalogenating enzymes and suggest that they contribute to the iodide-induced autoregulatory processes involved in the Wolff–Chaikoff effect.