Studies on the Elimination of Exogenous Lipids from the Blood Stream. Determination and Separation of the Plasma Triglycerides after Single Injection of a Fat Emulsion in Man

Single injection of a fat emulsion into the blood stream in man resulted into a complex eliminationcurve, when total triglyceride (TG) concentration in plasma was followed. The complexity of the curve was studied by separation of the plasma TG either by centrifugation or by a density gradient method with polyvinylpyrrolidone (PVP). Centri‐fugation of plasma at 48.6 times 10 4 G‐minutes did not solve the complex curves. The PVP method gave three TG fractions: fat emulsion in the top fraction and endogenous plasma TG in the bottom and middle fraction. Elimination curves obtained with the PVP method were compos‐site. The TG concentration in the top fraction, which was zero in fasting plasma, increased after injection of the emulsion and then decreased. This decrease could be resolved into a linear phase at high TG concentration and an exponential phase at lower concentrations. The curve for the bottom fraction showed a slowly increasing concentration and that for the middle fraction showed a rapid increase followed by a decrease. The complex appearance of the curve without fractionation of the TG depends on these two latter lipid fractions which change in concentration during the elimination. The difficulties in interpreting the elimination curves obtained by the centrifugation method was with the gradient shown to depend on heterogeneity in the top TG fraction obtained by centrifugation.