PLASMA PHOSPHOLIPID MASS-TRANSFER RATE - RELATIONSHIP TO PLASMA PHOSPHOLIPID AND CHOLESTERYL ESTER TRANSFER ACTIVITIES AND LIPID PARAMETERS

Human plasma phospholipid transfer protein (PLTP) has been shown to fa cilitate the transfer of phospholipid from liposomes or isolated very low and low density lipoproteins to high density lipoproteins. Its act ivity in plasma and its physiological function are presently unknown. To elucidate the role of PLTP in lipoprotein metabolism and to delinea te factors that may affect the rate of phospholipid transfer between l ipoproteins, we determined the plasma phospholipid mass transfer rate (PLTR) in 16 healthy adult volunteers and assessed its relationship to plasma lipid levels, and to phospholipid transfer activity (PLTA) and cholesteryl ester transfer activity (CETA) measured by radioassays. T he plasma PLTR in these subjects was 27.2 +/- 11.8 nmol/ml per h at 37 degrees C (mean +/- S.D.), and their PLTA and CETA were 13.0 +/- 1.7 mu mol/ml per h and 72.8 +/- 15.7 nmol/ml per h, respectively. Plasma PLTR was correlated directly with total, non-HDL, and HDL triglyceride (r(s) = 0.76, P < 0.001), total and non-HDL phospholipid (r(s), > 0.5 3, P < 0.05), and inversely with HDL free cholesterol (r(s) = -0.54, P < 0.05), but not with plasma PLTA and CETA. When 85% to 96% of the PL TA in plasma was removed by polyclonal antibodies against recombinant human PLTP-phospholipid mass transfer from VLDL and LDL to HDL was red uced by 50% to 72%, but 80% to 100% of CETA could still be detected. T hese studies demonstrate that PLTP plays a major role in facilitating the transfer of phospholipid between lipoproteins, and suggest that tr iglyceride is a significant modulator of intravascular phospholipid tr ansport. Furthermore, most of the PLTP and CETP in human plasma is ass ociated with different particles. Plasma PLTA and CETA were also measu red in mouse, rat, hamster, guinea pig, rabbit, dog, pig, and monkey. Compared to human, PLTA in rat and mouse was significantly higher and in rabbit and guinea pig was significantly lower while the remaining a nimal species had PLTA similar to humans. No correlation between PLTA and CETA was observed among animal species.