This is a study of the binding of the thyroid hormone (TH), triiodothyronine (T(,3)), to nuclei of red blood cells (RBCs) of Rana catesbeiana tadpoles. Specific binding activity was detected and the number of T(,3) binding sites per nucleus increased during spontaneous or T(,3)-induced metamorphosis. These results suggested that the binding sites are T(,3) receptors and that the increase in their number is a direct response of the RBCs to T(,3), a receptor induction. The proposal of receptor induction was investigated further. / The increase in the number of T(,3) binding sites after a T(,3) injection was completely inhibited by cycloheximide (CH) or actinomycin-D (act-D), inhibitors of protein synthesis and RNA synthesis, respectively. However, if either inhibitor was administered 48 hours or more after T(,3) injection the increase was not inhibited. The inhibitors were only effective when administered before T(,3) or within 24 hours after T(,3). This requirement for protein synthesis and RNA synthesis is typical of responses to thyroid hormone (TH) in amphibian metamorphosis. / When tadpole RBCs were incubated with T(,3) in vitro in M199, a nutrient rich medium, the number of nuclear T(,3) binding sites was constant during the first 24 hours and then increased over the next 24 hours. Increased T(,3) binding in vitro was highly sensitive to inhibition by CH (10('-6) M) or act-D (0.04 micrograms/ml). These results demonstrate that tadpole RBCs respond directly to T(,3) and that the increased T(,3) binding requires synthesis of RNA and protein in the RBCs. / Stimulation of increased nuclear T(,3) binding in vitro occurred over the same range of T(,3) concentration as occupation of the binding sites. The T(,3) binding sites had a high affinity for TH analogs which are very potent in stimulating metamorphic responses and a low affinity for analogs which are relatively inactive. These properties support the identification of the T(,3) binding sites as TH receptors. / The results of these studies support the concept of TH receptor induction by TH in tadpole RBCs during metamorphosis. / Source: Dissertation Abstracts International, Volume: 47-01, Section: B, page: 0187. / Thesis (Ph.D.)--The Florida State University, 1985.
| Identifer | oai:union.ndltd.org:fsu.edu/oai:fsu.digital.flvc.org:fsu_75763 |
| Contributors | THOMAS, CHARLES RICHARD., Florida State University |
| Source Sets | Florida State University |
| Detected Language | English |
| Type | Text |
| Format | 143 p. |
| Rights | On campus use only. |
| Relation | Dissertation Abstracts International |
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