Action of acetazolamide on the chick embryo during late development

Acetazolamide was injected into chick embryos on the 14th or 15th day of incubation. Doses ranging between 5 and 10 mg per egg produced a retardation in the growth of long bones. The affected bones contained a normal proportion of mineral as determined by ashing and presented a normal histological picture. On the basis of these findings, it is suggested that the alterations were not due to a specific direct effect of the drug on bones. The incorporation of 131-I by the thyroid glands of acetazolamide-injected embryos was analyzed radioautographically and quantitated on the same 6 mu-paraffin sections, with a thin window Geiger counter. The incorporation appeared notably reduced 3 h after the injection of acetazolamide and the reduction persisted for a least 24 h.the electron microscopical observation of thyroid follicular cells from similarly treated embryos showed that the cytological characteristics indicating an active protein synthesis were unmodified with respect to those found in control embryos. These results may indicate that acetazolamide inhibits the iodination of the throid hormone without interfering with the synthesis of the globulin. It is suggested that the growth retardation observed in the embryos treated with acetazolamide may be secondary to the action of the drug on the thyroid gland, although this action appears to be a transitory one.