The effect of radiation-induced anorexia on serum thyrotropin (TSH), pituitary TSH-β mRNA, pituitary TSH content, serum thyroxine (T4), and serum 3,5,3′-triiodothyronine (T3) was investigated using feed-matched controls. Rats received 10 Gy gamma whole-body irradiation and were examined 1-3 days postirradiation. Feed- matched and untreated controls were also studied. The average food intake of the irradiated and feed-matched groups was approximately 18% of the untreated controls. Over the three day period both the irradiated and feed-matched groups lost a significant amount of body weight. The serum T4 levels of both the irradiated and feed-matched groups were not significantly different from each other, but were significantly depressed when compared to the untreated control group. The serum TSH and T3 were, however, significantly greater in the irradiated than the feed-matched groups at day 3 posttreatment. To determine if the difference in the serum TSH level between the two groups was due to a pretranslational alteration in TSH production, we measured the TSH-β mRNA using an RNA blot hybridization assay. We found that the TSH-β mRNA level was the same in the irradiated and feed-matched groups, suggesting that the mechanism responsible for the radiation-induced increase in the serum TSH level is post- transcriptional. Pituitary TSH content in the irradiated rats was significantly less than in pair-fed controls, suggesting that irradiation may permit enhanced secretion of stored hormone.
ASJC Scopus subject areas
- General Biochemistry, Genetics and Molecular Biology
- Pharmacology, Toxicology and Pharmaceutics(all)