Influence of dietary protein on insulin-like growth factor binding proteins in the chicken.
We determined the effect of dietary protein on the distribution of insulin-like growth factor (IGF) binding proteins in chicken plasma. Three groups of male broilers (n = 6 per group) were fed (ad libitum) isocaloric diets containing 12, 21 or 30% dietary protein. Birds were fed respective diets beginning at 7 days of age and killed at 28 days. No differences were observed between adequate (21%) and high (30%) protein intakes for any of the parameters investigated (growth criteria, plasma levels of IGF-I, growth hormone or IGF-binding proteins). Feeding protein deficient diets (12%) resulted in a 34% decrease in body weight, 17% decrease in feed intake and a 39% increase in feed/gain ratio. IGF-binding proteins in plasma samples were separated by SDS-PAGE and transferred to nitrocellulose sheets. Nitrocellulose blots were probed with [125I]chicken IGF-II. Four regions of binding activity corresponding to 70, 43, 30 and 24 kDa were observed in all samples. Birds consuming 12% dietary group protein had less than 50% of the 43-kDa binding activity of birds consuming 21 or 30% dietary protein. The 30-kDa binding activity was 42% lower in the 12% dietary protein group compared to birds consuming adequate protein. In contrast, 70- and 24-kDa binding activities were not influenced by dietary protein. Chickens consuming 12% dietary protein had higher levels of growth hormone and lower levels of IGF-I than those consuming 21 or 30% dietary protein. These data indicate that in chickens, the circulating levels of at least two independent IGF-binding proteins are influenced by dietary protein.
Caperna
T J
TJ
US Department of Agriculture-Agricultural Research Service, Growth Biology Laboratory, Beltsville, MD 20705, USA. caperna@lpsi.barc.usda.gov
Rosebrough
R W
RW
McMurtry
J P
JP
Vasilatos-Younken
R
R
D000818:Animals; D001345:Autoradiography; D001835:Body Weight / Q000187:drug effects; D002645:Chickens / Q000254:growth & development*; D004044:Dietary Proteins / Q000494:pharmacology*; D013006:Growth Hormone / Q000097:blood; D018969:Insulin-Like Growth Factor Binding Proteins / Q000187:drug effects* / Q000378:metabolism*; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D007335:Insulin-Like Growth Factor II / Q000378:metabolism; D007457:Iodine Radioisotopes; D008297:Male
D004044:Dietary Proteins; D018969:Insulin-Like Growth Factor Binding Proteins; D007457:Iodine Radioisotopes; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II; D013006:Growth Hormone