Metabolism of i*C-Labelled Steroids 7 



was prepared from [21-^*C]-21-diazoprogesterone by the 

 action of hydriodic acid, and [21-^^C]-DCA from the same 

 labelled intermediate by treatment with acetic acid. 21- 

 Diazoprogesterone was prepared from 3-keto-J*-etiocholenone 

 chloride by an improved Arndt-Eisert synthesis. 



(2) Mode of Administration. After trying a variety of 

 solvents and doses, the following procedure was adopted. A 

 dose of 1 mg. of radioactive steroid is dissolved in 0-25 ml. 

 ethyl laurate and injected at 9 p.m. intramuscularly in the 

 neighbourhood of the head of the femur. Immediately after 

 injection the animals are placed in a metabolism chamber 

 without food or water. The air circulating through the 

 chamber is first freed of CO2 by being passed through barium 

 hydroxide solutions. The air coming from the chamber is 

 circulated through two sodium hydroxide bottles for trapping 

 the CO2 exhaled by the animals. Contact of the feet of the 

 animals with the floor of the chamber is prevented by a wire 

 sheet, in such a way that the urine falls to the bottom but 

 the faeces are retained on the wire. 



All the animals used for complete distribution studies were 

 sacrificed twelve hours after injection by exsanguination from 

 the inferior vena cava under ether anaesthesia. In addition, 

 5 mice were given 1 mg. of oestrone, and the faeces and urine 

 were collected for 144 hours, after which the animals were 

 sacrificed. CO2 was collected for the first 12 hours and again 

 for 12 hours starting at 97 hours after injection. Five mice 

 were similarly treated with progesterone and 5 other mice 

 with DCA. 



(3) Preparation of Samples of Tissues and Excreta for 

 Counting. In the animals sacrificed 12 hours after injection, 

 about 40 tissues and excreta were examined with the Geiger 

 counter. In the animals sacrificed at 144 hours, only plasma, 

 kidney, adrenal, thyroid, hypophysis, liver and gall bladder 

 were investigated. The organs were removed from the animals 

 and the excreta digested in sodium hydroxide, plated on a 

 brass planchette and the plates carbonated. The more reliable 

 results were obtained with infinitely thick preparations 



