Active immunization with a synthetic peptide region of growth hormone: increased lean tissue growth.

The effects of active immunization against a specific peptide region of GH (sequence 134-154) were examined in a species relevant for animal production in vivo. Peptide-immunized lambs exhibited significant increases in carcass protein and water contents and consequently increased carcass weight. The comparatively smaller increases in carcass water and protein contents which occurred in GH-treated lambs were offset by decreased fat accretion. Thus, even though peptide immunization improved lean tissue growth, it did not simply enhance all actions of GH or mimic exogenous hormone administration. This is the first definitive demonstration that endogenously produced antibody may enhance endogenous hormone activity and performance in animals.