Cartilage response to thyroid hormones in the sex-linked dwarf chicken

1. Trachea cartilages were dissected from normal and dwarf chickens which had been injected with thyroxine (T4, 200 micrograms/kg) or triiodothyronine (T3, 200 micrograms/kg) for seven consecutive days, and were analysed for nucleic acids, proteins and polyamines. 2. In saline-injected control chickens, RNA, but not DNA and protein, concentration of the cartilage was higher in dwarfs than in normals. The concentration of putrescine was lower in dwarfs than in normals, while that of spermine was the reverse. 3. Thyroid hormones, especially T3, tended to increase concentrations of RNA, spermidine and spermine, and to decrease that of putrescine. However, there were no clear differences in the response to hormones between breeds.