PLASMA-CONCENTRATIONS OF GH AND IGF-I IN GREAT-DANE RAISED ON FOOD WITH DIFFERENT PROTEIN OR MINERAL-CONTENT

Six groups of young giant breed dogs, Great Danes, were raised on food differing in content of either protein (13%, 21% or 30%) or mineral(1 .1% Ca and 0.9% P, 3.3% Ca and 0.9% P or 3.3% Ca and 3.0% P), but not in energy. Plasma GH and IGF-I concentrations were determined during t he study, i.e. from the 6th to the 26th week for the protein groups an d to 17 weeks for the mineral groups. When compared with miniature poo dles, the Great Danes had significantly higher levels of GH and IGF, t he former decreasing with age. Low protein intake as well as high Ca i ntake (but not high Ca and high P intake) were associated with decreas ed IGF-I but not with different GH levels, when compared with the cont rol dogs. Low protein intake may result in decreased hepatic IGF-I syn thesis. Hypoparathyroid-induced decreased autocrine and paracrine IGF- I formation in the dogs with high Ca intake and slower growth rate is discussed.