The possible involvement of cholesterol (CHOL) in the cellular transformations leading to the acquisition of the multidrug-resistance (MDR) phenotype has been evaluated in human ovarian cancer cells. To this end, the A2780 cell line and the 52-fold doxorubicin (DX)-resistant counterpart A2780-DX3 were analyzed under two different growth conditions: standard culture medium (FCS medium), or medium deprived of CHOL (LPDS medium). The following variables were investigated: free and esterified cytoplasmic membrane CHOL, cell growth, DX uptake and cytotoxicity, and low-density lipoprotein uptake and degradation (as indirect variables of CHOL homeostasis). The impact of the calcium antagonist verapamil (VER) on these variables was assessed. The results obtained indicate that under standard growth conditions, A2780 and A2780-DX3 cells are different not only with respect to DX uptake and sensitivity, but also with respect to membrane CHOL content and the ratio of free-to-esterified CHOL. The deprivation of lipoproteins in the culture medium, apart from slowing cell growth, induced a decrease in the cytoplasmic membrane CHOL content (mainly of the esterified form) that was particularly evident in A2780 sensitive cells. In LPDS medium, a reduced DX uptake occurred in both cell lines, but to a greater extent in A2780 cells, in which DX cytotoxicity decreased to values comparable to that of A2780-DX3 resistant cells. Restoration of DX sensitivity was achieved with the addition of 10 microM VER.(ABSTRACT TRUNCATED AT 250 WORDS)