TRANSFER OF CHOLESTEROL BETWEEN HIGH-DENSITY-LIPOPROTEINS AND CULTURED RAT SERTOLI CELLS

In the testes, the Sertoli cells are separated from the blood capillar ies by the basement membrane, thereby excluding the passage of low den sity lipoproteins (LDLs) but allowing the passage of high density lipo proteins (HDLs). The present study examines first the capacity of Sert oli cells to uptake cholesterol from HDL and secondly the role of apol ipoproteins (apo) A-I and E in cholesterol flux between HDL and cultur ed rat Sertoli cells. In the presence of HDL in cultured medium, rat S ertoli cells accumulated few amounts of esterified cholesterol. Incuba tion of [C-14]cholesterol-labelled Sertoli cells with [H-3]cholesterol -labelled HDL showed that the amount of cholesterol influx slightly ex ceeded its efflux, thus resulting in a net uptake of cholesterol from HDL to rat Sertoli cells. The amount of HDL-cholesterol converted to s teroids by Sertoli cells was about 32% of influx. Uptake of cholestero l by Sertoli cells was three times higher with phospholipid - apo A-I vesicles and seven times higher with phospholipid - apo E vesicles tha n that with phospholipid vesicles without apolipoprotein. Phospholipid - apo A-I vesicles promoted cholesterol efflux at the same rate as na tive HDL and twice as efficiently as phospholipid - apo E vesicles. Th us, this study shows that rat Sertoli cells have the capacity to take up HDL-cholesterol for membrane renewal and steroid production mainly by apo E dependent pathways