Relationship of serum immunoreactive somatomedin-C to dietary protein and energy in growing rats.
Protein-energy undernutrition has its most devastating consequences during growth. Postal somatic growth now appears to be regulated in large part by the somatomedins, a family of growth hormone-dependent peptide mitogens. This study, using growing rats as the model, was designed to determine the relationship between protein and energy intake and serum immunoreactive somatomedin-C. Four-week-old male Sprague-Dawley rats were fed ad libitum three levels of isoenergetic protein diets (5%, 10%, and 15% lactalbumin) at each of three levels of energy (ad libitum, 75% or 50% of ad libitum quantities). Dietary fat was held constant at 11.9% as cottonseed oil. At 5 weeks of age, serum somatomedin-C concentration was predominately influenced by the dietary protein and increased linearly as protein intake increased from 5% to 15%. at 6, 9, and 12 weeks of age, serum somatomedin-C concentration was influenced by both protein and energy intake, although protein intake appeared to be the more important variable. Serum somatomedin-C was highly correlated with both body weight (r = 0.84, P less than 0.001) and tail length (r = 0.74, P less than 0.01). These results indicate that measurement of immunoreactive somatomedin-C provides a valuable biochemical index of protein-energy nutriture.
D000818:Animals; D004032:Diet; D004044:Dietary Proteins / Q000378:metabolism*; D004435:Eating; D004734:Energy Metabolism; D007334:Insulin-Like Growth Factor I; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains / Q000254:growth & development*; D013002:Somatomedins / Q000378:metabolism*
D004044:Dietary Proteins; D013002:Somatomedins; D007334:Insulin-Like Growth Factor I