We have examined the effects of chronic thyroid hormone deficiency, vitamin A deficiency, and subsequent acute repletion with thyroid hormone (T3) and/or retinoic acid (RA) on the expression of hepatic apolipoprotein (ape) A-I mRNA. Chronically hypothyroid and/or retinoid-deficient male Lewis rats were treated once or three times with T3, all-trans-RA, or both hormones. The hypothyroid state significantly reduced (P < 0.001) and the vitamin A-deficient state significantly elevated (P < 0.0001) the expression of apo A-I mRNA. A single injection of T3 (10 μg/100 gm body weight) significantly elevated apo A-I mRNA in hypothyroid rats (P < 0. 001). A single injection of RA (20 μg/rat) reduced apo A-I mRNA by about 20 to 25% and daily injection of RA for three days reduced apo A-I mRNA abundance further in hypothyroid (P < 0.05), but not euthyroid rats. There was a significant interaction between T3 hormone treatment and vitamin A status of the rats, as well as between RA and T3 treatment and the thyroid status of the rats. These in vivo results may indicate that nuclear retinoid receptors and thyroid hormone receptors interact in the regulation of the apo A-I gene in liver.
All Science Journal Classification (ASJC) codes
- Endocrinology, Diabetes and Metabolism
- Molecular Biology
- Nutrition and Dietetics
- Clinical Biochemistry