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Vitamin A deficiency and tri-iodothyronine action at the cellular level in the rat
P Higueret1, I Pailler, H Garcin
1Département Alimentation et Nutrition, Université de Bordeaux I, Talence, France.
Abstract:
Young rats were given a diet with or without vitamin A for a period of 7 weeks. In rats on the vitamin A-deficient diet, the formation of tri-iodothyronine (T3) complexes with nuclear proteins was reduced, and Scatchard analysis showed a decreased capacity of nuclear T3 receptors. In these rats, a decrease in growth and a decrease in the activity of lipogenic enzymes (glucose-6-phosphate dehydrogenase, phosphogluconate dehydrogenase and L-malate dehydrogenase) occurred, which could be related to the decreased formation of T3-nuclear protein complexes.
Insights
Vitamin A deficiency in young rats impaired tri-iodothyronine (T3) binding to nuclear proteins, reducing T3 receptor capacity. This vitamin A deficiency led to decreased growth and lipogenic enzyme activity.
Area of Science:
- Biochemistry
- Endocrinology
- Nutritional Science
Background:
- Vitamin A is essential for numerous physiological processes.
- Thyroid hormones, like tri-iodothyronine (T3), regulate metabolism and growth.
- The interaction between vitamin A and thyroid hormone action is not fully understood.
Purpose of the Study:
- To investigate the impact of vitamin A deficiency on tri-iodothyronine (T3) nuclear receptor binding.
- To examine the relationship between vitamin A status, T3 receptor function, and metabolic enzyme activity in rats.
Main Methods:
- Young rats were fed either a vitamin A-sufficient or vitamin A-deficient diet for 7 weeks.
- Nuclear proteins were isolated to assess T3 complex formation with receptors.
- Scatchard analysis was employed to determine the capacity of nuclear T3 receptors.
- The activity of key lipogenic enzymes was measured.
Main Results:
- Vitamin A-deficient rats exhibited reduced formation of tri-iodothyronine (T3) complexes with nuclear proteins.
- Scatchard analysis revealed a decreased capacity of nuclear T3 receptors in vitamin A-deficient rats.
- These rats showed diminished growth rates and reduced activity of lipogenic enzymes, including glucose-6-phosphate dehydrogenase, phosphogluconate dehydrogenase, and L-malate dehydrogenase.
Conclusions:
- Vitamin A deficiency negatively affects the binding of tri-iodothyronine (T3) to its nuclear receptors.
- Impaired T3-nuclear protein complex formation may underlie the observed decreases in growth and lipogenic enzyme activity in vitamin A-deficient rats.
- This study highlights a potential mechanism linking vitamin A status to thyroid hormone-mediated metabolic regulation.