Morphometric and electron microscopic studies of goiter induced by lithium in the rat

Abstract

Abstract Fifty‐two male and female albino rats were used. Lithium‐treated rats (30 animals) received twice daily intraperitoneal injections of lithium carbonate (40 mg/kg body weight) for 80 days. Three control groups were used. The first remained uninjected; the second received sodium chloride solution equal in volume and tonicity to the lithium carbonate solution; the third received sodium carbonate solution in which the carbonate ion concentration was equivalent to that in the lithium carbonate solution. Thyroid weights were analyzed as wet and dry weights, and as wet and dry thyroid weights in milligrams per 100 gm body weight. Morphometric or electron microscopic studies were carried out on Epon‐embedded tissue routinely prepared for light or electron microscopy. Thyroid weights and values were greater in lithium‐treated animals. A sex‐related effect of lithium was indicated. The differences in thyroid weights between lithium‐treated and control male rats were greater than those between female lithium‐treated and control rats. Morphometric analysis revealed an increase in the mean diameter of sections of follicles and relative amounts of colloid, and a decrease in follicular cell heights in lithium‐treated animals. The electron microscope revealed an enlarged Golgi apparatus in many thyroid follicular cells of lithium‐treated rats. The enlargement of the Golgi apparatus was most evident in male lithium‐treated animals. The relationship of these findings to the mechanism of lithium action was briefly discussed.