Representative photomicrographs of mammary-gland whole mounts after implantation with neutralizing antibody to HGF. Immature, 5-week-old (a,b) or adult, 12-week-old (c,d) female mice were given implants of Elvax pellets containing anti-HGF antibody (HGF AB) (4 μg/implant) in the right inguinal mammary gland (b,d) or a control (C) Elvax pellet containing normal serum in the contralateral left inguinal gland (a,c) and were then given daily injections of estrogen + progesterone for 6 days. In addition, adult 12-week-old female mice were given two Elvax pellets implanted side by side, one containing estrogen+R5020, the other containing HGF AB (e). In all cases, whole mounts were prepared 7 days later. Note reduced size of endbuds (indicated by arrows) in the immature gland with implanted HGF AB (b) in comparison with the control (C)-implanted gland in (a) (arrowheads). Note the presence of side-branches in control (C)-implanted adult gland (c) (arrowheads) and their absence in glands with HGF AB implants (d) (arrows). Note the presence of side-branches near the estrogen+R5020 implant (indicated by arrowheads) and their absence near the antibody implant (e) (arrows). C, control; E, estrogen; HGF, hepatocyte growth factor; HGF AB, anti-HGF antibody.