The use of a non-ionic detergent (Triton WR 1339) to determine rates of triglyceride entry into the circulation of the rat under different physiological conditions.

1. The concentration of triglyceride in the plasma rises linearly for 3 hr after the intravenous injection of the non-ionic detergent, Triton WR 1339, in the rat.2. Minimum rates of triglyceride entry into the plasma have been calculated from measurements of the plasma triglyceride concentration at 1.5 hr after Triton injection. These are 30 and 52 mumoles/hr.200 g body weight respectively for male and female animals on a stock laboratory diet and 25 and 33 mumoles/hr.200 g body weight respectively for male and female animals starved for 48 hr. The values may have to be increased by 10 or 20% to take account of a small leak of triglyceride from the plasma in animals injected with Triton and of an effect of ether anaesthesia on the rate of entry of triglyceride into the plasma.3. Substitution of the stock laboratory diet by diets that are lower in fat content does not alter significantly the rate of triglyceride accumulation in the plasma after Triton injection.4. There is no change in the triglyceride content of the livers of male and female rats at 24 hr after Triton injection. At 6 hr after Triton, the liver triglyceride content of female rats which have been fed their normal diet is increased.