Albumin activates TGF-β pathway. A , Albumin and TGF-βRII immunoprecipitations. Samples treated or untreated with serum albumin were coimmunoprecipitated with antibodies directed against albumin or TGF-βRII. All samples were then probed with an anti-TGF-βRII antibody. The band at 50 kDa is the heavy chain of the precipitating antibody. B , Western blot analysis of Smad2-P 24 and 48 h after albumin treatment. Each band represents a different animal (24 h: controls, n = 2; albumin, n = 3; 48 h: controls, n = 2; albumin, n = 4).