Abstract The liver is the major site of cholesterol syn- thesis and metabolism, and the only substantive route for eliminating blood cholesterol. Scavenger receptor class B, type I (SR-BI) has been reported to be responsible for mediating the selective uptake of high-density lipopro- tein cholesteryl esters (HDL-CE) in liver parenchymal cells (PC). We analysed the expression of SR-BI in iso- lated rat liver cells, and found the receptor to be highly expressed in liver PC at both the mRNA and protein lev- els. We also found SR-BI to be expressed in liver endo- thelial cells (LEC) and Kupffer cells (KC). SR-BI has not previously been reported to be present in LEC. CD36 mRNA was expressed in all three liver cell types. Since caveolin-1 appears to colocalize with SR-BI and CD36 in caveolae of several cell lines, the distribution and ex- pression of caveolin-1 in the liver cells were investigat- ed. Caveolin-1 was not detected in PC but was found in both LEC and KC. This led to the suggestion that caveo- lin-1 may be more important in the efflux of cholesterol than in the selective uptake of cholesterol in the liver. Keywords SR-BI · Caveolin · Hepatic lipase · Liver endothelial cells · Rat (Wistar) · Mouse (MF1) Abbreviations BCA: bicinchoninic acid · BSA: bovine serum albumin · CE: cholesteryl ester · Cla-1: CD36 and LIMPII analogue 1 · DMEM: Dulbecco’s modified essential medium · ECL: enhanced chemiluminescence · EMEM: minimal essential Eagle’s medium · HDL: high-density lipoprotein · HL: hepatic lipase · HRP: horseradish peroxidase · KC: Kupffer cells · LDL: low-density lipoprotein · LEC: liver endothelial cells · NEAA: non-essential amino acids · PBS: phosphate-buffered saline · PC: liver parenchymal cells · RT-PCR: reverse transcription-polymerase chain reaction · SR-BI/II: scavenger receptor class B type I/II Introduction Many epidemiological studies have established that ele- vated plasma LDL cholesterol levels are related to the development of cardiovascular disease, whereas this risk is inversely proportional to plasma HDL cholesterol lev- els (Gordon and Rifkind 1989). It has been known for some time that liver cells and other cells such as cells in the adrenal cortex, the testis and the ovary are capable of taking up cholesterol from HDL without degrading the entire lipoprotein particle (Glass et al. 1983; Glass et al. 1985). The liver is the main route for removing HDL from the blood. The interaction between HDL and hepa- tocytes results in selective cellular uptake of CE (Glass et al. 1985; Johnson et al. 1986; Pittman et al. 1987) and the protein moiety therefore serves as a carrier that trans- ports cholesterol from extrahepatic tissues to the liver (Pieters et al. 1994b). Recent evidence suggests that the binding of HDL may be mediated by a member of the scavenger receptor family (SR-BI) (Acton et al. 1996). Two distinct iso- forms of class B receptors, SR-BI and SR-BII, that differ by alternative splicing in the C-terminal region, have been identified (Murao et al. 1997; Webb et al. 1997). SR-BII also mediates cholesterol transfer between HDL and cells, but with lower efficiency than SR-BI (Webb et al. 1998). Evidence supporting a role for SR-BI in the binding of HDL in cells includes its tissue distribution pattern, which is coincident with that of selective uptake of CE from HDL, and the observation that SR-BI expres- sion in the adrenals is strongly associated with the intra- cellular cholesterol level (Wang et al. 1996). We gratefully acknowledge the financial support of The Norwe- gian Research Council, The Norwegian Council of Cardiovascular Disease, The Norwegian Cancer Society and the Anders Jahres Foundation. L. Malerød · L.K. Juvet · T. Berg ( ✉ ) Division of Molecular Cell Biology, Department of Biology, University of Oslo, P.O. Box 1050 Blindern, 0316 Oslo, Norway e-mail: trond.berg@bio.uio.no Tel.: +47-228-54596, Fax: +47-228-54605 T. Gjøen Division of Microbiology and Cell Biology, Department of Pharmacy, University of Oslo, P.O. Box 1068 Blindern, 0316 OSLO, Norway Cell Tissue Res (2002) 307:173–180 DOI 10.1007/s00441-001-0476-9 REGULAR ARTICLE Lene Malerød · Lene Kristine Juvet · Tor Gjøen Trond Berg The expression of scavenger receptor class B, type I (SR-BI) and caveolin-1 in parenchymal and nonparenchymal liver cells Received: 24 April 2001 / Accepted: 17 September 2001 / Published online: 4 December 2001 © Springer-Verlag 2001