Functional Relationships Among Hypothalamus, Pituitary and Thyroid Glands in Anuran Amphibians

Authors: Kadriye Akgün DAR

Abstract: In this study, the effects of thyroxine, thyrotrophin-releasing hormone (TRH) and prophylthiouracil on he hypothalamic neurosecretory (NS) cells, thyrotropic (TSH) celis and thyroid glands of Rana ridibunda and Bufo viridis were investigated. Cells of the preoptic nukleus were classified into smaller and Iarger NS cells. It was found that NS cells occupy a Iarger area in Bufo than in Rana, and that smaller NS cells were more affected by the employed substances. In the Iight of the obtained data and Iiterature on this subject, it was concluded that these smaller NS cells may produce TRH. TSH cells in pars distails of hypophysis were observed to show a similar distribution in either species, and to be placed in the whole periphery and exceedingly in posterior part. In addition, it was found that exogeneous TRH is effective in the hypothalamus, TSH cells and thyroid gland in investigated Amphibians. On the other hand, the data reveal that the release of the material synthesized in the follicle cells of thyroid gland into the humen occurs in apocrine way. Results of the study show that Rana is more sensitive to the treated substances than Bufo.

Keywords: Thyrotropin releasing hormone (TRH), Thyroxine, Propylthiouracil, Hypothalamus, Hypophysis, Thyroid, Rana ridibunda, Bufo viridis, (Anura)