Protective effects of thyroid hormones on atherosclerotic formation in rabbits

Abstract

The objective of this investigation was to study the protective effectives of thyroid hormones on atherosclerotic formation in rabbits. This experiment was performed in twenty-five male New Zealand Whilte rabbits weighing between 2.0-2.5 kg. The animals were randomly divided into five groups, each group containing 5 animals. The rabbit model of atherosclerosis was induced with a period of twelve weeks. Group I, rabbits were fed with standard chow daily. Group II, rabbits were fed with lipid rich food (containing: standard chow, 4% coconut oil, 1% cholesterol). Group III, rabbits were fed with lipid rich food plus propylthiouracil (PTU) at the dose of 20 mg/kg body weight daily. Group IV, rabbits were fed with lipid rich food, 20 mg/kg of PTU, and 50 [microgram]/kg of L-thyroxine (T[subscript 4]) daily. Group V, rabbits were fed with lipid rich food, 20 mg/kg of PTU, and 0.6 [microgram]/kg of Triiodothyronine (T[subscript 3]) daily. Body weight and body temperature were measure weekly. Blood samples were collected for measurements of serum lipid profile, thyroid hormones and lipid oxidation. At the end of the experiment, animals were euthanized and vascular tissues were collected for measurement of histological analysis. Our results showed that animals in group IV had significant decreases in malondialdehydes in plasma and low density lipoprotein (LDL) contents, compared to animals in group II and III. Animals in group IV and V had lower ratio of areas of atherosclerotic lesion and compositions of atherosclerotic lesions, compared to animals in group II and III. In conclusion, the present study demonstrates that thyroxine and triiodothyronine have protective effect by inhibiting atherosclerotic formation in a rabbit model.