Electroimmunoassay of rat apolipoproteins A-I, A-IV, and E. A procedure for sample treatment to increase the sensitivity in diluted fractions

Methods for the quantitative determination of rat apolipoproteins A-I, A-IV, and E by electroimmunoassay are described. Apolipoproteins present in diluted samples of biological fluids (approx. 2 ml) were concentrated by precipitation with deoxycholate and trichloroacetic acid. The protein pellets were solubilized in 0.1 ml of 0.5 M NaOH and these samples were delipidated with tetramethylurea and assayed. This protocol enables the measurement of apolipoprotein concentrations that are at least 10 times lower than normally detectable; 0.2 micrograms of apolipoprotein A-IV, 0.2 micrograms of apolipoprotein A-I, and 0.8 micrograms of apolipoprotein E can be easily detected in samples of 2 ml.