Abstract
Rats were administered orally with B_2-Nic^<*1)>-^3H (only nicotinate moieties were uniformly labeled), and the incorporation of radioactivity into blood stream and into NAD of the kidney and the liver was investigated. A very slow increase in the specific radioactivity was observed with free NiA^<*2)>-^3H. After 30 hours of administration, however, the specific radioactivity of blood nicotinate of rats administered with B_2-Nic-^3H became higher than that of rats administered with NiA-^3H, suggesting the deposit type nature of the former compounds. The rate of incorporation of radioactivity of B_2-Nic-^3H into NAD of organs was also found to be slow as compared with the rate of incorporation of NiA-^3H. However, B_2-Nic-^3H was found to be superior to NiA-^3H in keeping the high level of specific radioactivity of hepatic and renal NAD for a long time.
