Cholesterol and cholesteryl ester concentration in different size classes of cultured human fibroblasts: effect of in vitro aging.

Early and late passage WI-38 fibroblasts were fractionated on the basis of cell size by gravity sedimentation, and free and esterified cholesterol concentrations were determined in each fraction. The cholesteryl ester concentration in all size classes of late passage cells was greater than that of all size classes of early passage cells; the average of all fractions of late passage cells was 2.5 times greater (pg/micrometers 3) and 1.7 times greater (micrograms/mg protein) than that of all fractions of early passage cells (p less than 0.001). The average free cholesterol concentration (micrograms/mg protein) in late passage cell fractions exhibited a consistent, but not statistically significant, increase over that in early passage cells. These results indicate that the increase in cholesteryl ester concentration in late passage WI-38 fibroblasts is not solely attributable to the large, non-dividing cells which accumulate in senescing cultures.