Separation of wasting syndrome and lethality caused by 2,3,7,8-tetrachlorodibenzo-p-dioxin

Twenty rats were administered LD50 doses of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) i.p. (60 micrograms/kg). Two days later 10 rats were started and maintained on a diet containing 5% hexadecane, whereas the other 10 rats continued receiving basal diet. Dietary hexadecane increased the mortality rate of rats from 60 to 100%. All animals destined to die showed a biphasic body weight and food intake pattern. The first 16 days after dosing were characterized by progressive weight loss which went hand in hand with increasing appetite suppression. No animal died during this initial phase. After day 16, rats overcame their loss of appetite, started eating and stabilized their body weight. During this second phase, lasting from day 16 to day 40, mortality progressed to 60 and 100% in the controls and hexadecane-treated rats, respectively. No body weight loss or change in food intake was observed in any of the surviving animals. Data indicate that TCDD-induced wasting syndrome is due to appetite suppression. However, wasting syndrome does not seem to be the ultimate cause of lethality.