INFLUENCE OF GONADS ON THE CHANGES OF THYROID GLAND FUNCTIONS PRODUCED BY CHOLESTEROL-ENRICHED DIET IN RATS

Publisher Summary This chapter discusses experiments to study the influence of gonads on the changes of thyroid gland functions produced by cholesterol-enriched diet in rats. Experiments were carried out in male and female Sprague–Dowley rats, selected immediately after weaning (three weeks after birth). Total castration was done by surgery, and one week later cholesterol feeding was initiated. Female animals were injected subcutaneously with substitutive doses of 17-β-estradiol (E 2 ) and male rats injected subcutaneously with testosterone propionate (TP). During a 30-day period, a semisynthetic diet containing 52.8 g% carbohydrates, 27.6 g% proteins, 14.6 g% fats, and 470 kcal% was provided. Cholesterol was added, 1 g% with 0.1 g% beef dessicated bile. Animals were sacrificed by acute bleeding under slight ether anesthesia. Plasma samples were stocked in freezer below −20°C until plasma usage. It was found that when male rats were submitted to a high-cholesterol diet for thirty days, an enhanced I 131 uptake by the thyroid gland was determined either 1 h after the administration of PTU or 24 h after the injection of radioactive iodine. Increased levels of plasma PBI (24 h after I 131 administration) were also found; these effects suggest an increasing formation of thyroid hormones.