title: The role of plasma-binding proteins in the cellular uptake of lipophilic vitamins and steroids.
abstract: Steroid hormones and many other lipophilic compounds are believed to enter cells solely by free diffusion through the plasma membrane. However, recent work using a megalin-deficient mouse model has identified a new endocytic pathway responsible for the delivery of steroids to renal and gonadal tissues. This review describes these new pathways for uptake of 25-hydroxy-vitamin-D3 and the gonadal sex-steroids (17beta-estradiol and testosterone) bound to vitamin D-binding protein and sex hormone-binding globulin respectively. Furthermore examples of other lipophilic molecules that enter cells by receptor-mediated pathways will be presented and the receptors responsible for their uptake described.
authors.affiliation: Department of Medical Biochemistry, University of Aarhus, Denmark. tka@biokemi.au.dk
authors.forename: T K
authors.initials: TK
authors.lastname: Andreassen
mesh_terms: D000818:Animals; D004285:Dogs; D005260:Female; D006801:Humans; D008297:Male; D051379:Mice; D011247:Pregnancy; D011485:Protein Binding; D011817:Rabbits; D051381:Rats; D012712:Serum Globulins / Q000378:metabolism; D012738:Sex Hormone-Binding Globulin / Q000378:metabolism*; D015398:Signal Transduction; D013256:Steroids / Q000378:metabolism*; D014809:Vitamin D-Binding Protein / Q000097:blood; D014815:Vitamins / Q000378:metabolism*
chemical_list: D012712:Serum Globulins; D012738:Sex Hormone-Binding Globulin; D013256:Steroids; D014809:Vitamin D-Binding Protein; D014815:Vitamins