(A) Immunoblot of pooled microsomes prepared from human liver, breast, and colon (25 μg per lane), and probed with polyclonal antibody to b5R. First 3 lanes of panel A: 0.32, 0.16, and 0.0.08 pmol human recombinant b5R. (B) Immunoblot of pooled microsomes prepared from human liver (10 μg per lane), breast (50 μg), and colon (50 μg), and probed with polyclonal antibody to cyt b5. First 3 lanes of panel B: 0.42, 0.21, and 0.11 pmol human recombinant cyt b5. 12% polyacrylamide gels.