THYROID FUNCTION IN MOLYBDENOTIC RABBITS

Abstract

SUMMARY The endocrine activity of the thyroid glands of rabbits fed a diet containing 0·3% molybdate ion for 25 and 31 days was evaluated. Means (± s.e.m.) were plasma thyroxine (T4) concn (μg/100 ml): 15 molybdate-fed rabbits, 2·31 ± 0·34; 19 control rabbits, 4·40 ± 0·34. T4 distribution space (ml/100 g body wt): molybdate-fed rabbits, 21·5±2·1; controls, 21·4 ± 0·9. T4 secretion rate (μg/24 h/100 g): molybdate-fed rabbits, 0·320 ± 0·073; controls, 0·601 ± 0·046. Histometric measurements made on photographs of gland sections showed that the follicular epithelial cells formed 12·8% of the total area in molybdate-fed rabbits and 25·8% in controls. The histological appearance of the sections was one of increased colloidal storage and of epithelial inactivity in the molybdate-fed rabbits. Comparisons with glands from a food-restricted group of rabbits supported the view of thyroidal hypofunction in molybdenosis in rabbits, with reduced food intake as the major causal factor. Some additional degeneration of the thyroid gland was attributed directly to the molybdate ion.