<正> Cholesterol

a major lipid component of plasma membrane

is thoughtto have profound effects on the structure and function of cells.Mostanimal tis-sues are capable of synthesizing cholesterol de novo from acetate;however

thereare relatively few mammalian cells in vitro expressing an absolute requirement foran exogenous source of cholesterol.In this paper

it was shown that IR983F（983）rat myeloma cells and P3X63-AgS-U1（P3U1）and P3X63-Ag8.653（653）mousemy eloma cells which had been cultivated in serum-free medium for more than 6months required cholesterol in vitro for growth in serum-free medium.Optimalgrowth of P3U1

653 and 983 occurred in cholesterol concentration of 5

10 and15μg/ml

respectively.Moreover

it was demonstrated that the cholesterol couldbe replaced by human low density lipoprotein in a concentration of 10μg/ml butnot by mevalonic acid lactone.In contrast to the parental myeloma cells

hybridoma cells derived from the mouse myeloma cells which had been cultivatedin serum-free medium for more than 6 months did not require cholesterol.