Direct determination of apolipoprotein C-III specific activity using immunoaffinity chromatography

This chapter presents the direct determination of apolipoprotein c-III specific activity using immunoaffinity chromatography. This chapter explains that because of their similar molecular weights and solubility characteristics, purification of the individual C apolipoproteins from the limited amounts of material available in a small plasma sample is extremely difficult. A method for performing turnover studies of apoC which utilizes isoelectric focusing to separate apoC-II from apoC-III has been discussed in this chapter. This chapter also presents a new method for studying the metabolism of apoC-III, which employs immunoaffinity chromatography to isolate this apolipoprotein from lipoprotein fractions in small plasma samples for determination of specific radioactivity. This chapter explores that for a given ratio of the apoC-III specific activity between very low-density lipoprotein (VLDL) and high-density lipoprotein (HDL) observed in vivo following the injection of radioiodinated VLDL, the fraction of apoC-III in VLDL which can participate in the equilibration process is negatively correlated to the fraction of equilibrating apoC-III in HDL. Any kinetic system proposed to explain the metabolism of apoC-III in man addresses this relationship.