Western ligand and immunoblot analysis of amniotic fluid hIGFBP-1. (a) Western ligand blot of amniotic fluid from transgenic (tg) and wild-type (wt) fetuses from F+/M– matings. Human IGFBP-1 migrates with an apparent molecular weight of 30–32 kDa. A high-molecular-weight IGFBP (40–46 kDa) whose size is consistent with that of variantly glycosylated IGFBP-3 was also detected. (b) Western immunoblot analysis of amniotic fluid from the membrane shown in a using a mouse anti–hIGFBP-1 monoclonal antibody (mAb 6305). e, embryonic day.