Factors Affecting Extractability of Cholesterol from Lyophilized Sera by Cold Chloroform. ∗

Summary

A study has been conducted on factors which affect the “readily extractable” cholesterol concentrations in serum. The results showed that (a) in general, REC values increased as triglyceride and cholesterol contents of the serum and chylomicra increased, but a notable exception was high REC values in nephrotic subjects in whom chylomicron contents of cholesterol and triglyceride were low, (b) addition of the sodium salts of long chain fatty acids to serum prior to lyophilization markedly increased cholesterol extractability, (c) addition of crystalline human serum albumin to sera with high REC concentrations markedly reduced REC values; the albumin also reduced REC concentration in most normal sera but in no case did it completely disappear, (d) traces of moisture in the chloroform used for the extraction had little or no effect on most sera with low REC concentration but markedly increased it in sera with high REC concentration. It is suggested that the concentration of non-albumin bound free fatty acids may play a major role in regulating REC concentrations in various sera.