In vitro lipid metabolism, growth and metabolic hormone concentrations in hyperthyroid chickens.
Indian River male broiler chickens growing from 7 to 28 d of age were fed on diets containing energy:protein values varying from 43 to 106 MJ/kg protein and containing 0 or 1 mg triiodothyronine (T3)/kg diet to study effects on growth, metabolic hormone concentrations and in vitro lipogenesis. In vitro lipid synthesis was determined in liver explants in the presence and absence of ouabain (Na+, K(+)-transporting ATPase (EC 3.6.1.37) inhibitor) to estimate the role of enzyme activity in explants synthesizing lipid. Growth and feed consumption increased (P < 0.01) when the energy:protein value decreased from 106 to 71 MJ/kg protein; however, both variables decreased as the value was further decreased from 53 to 43 MJ/kg protein. Triiodothyronine depressed (P < 0.01) growth, but not food intake. Large energy:protein diets (> 53 MJ/kg protein) and dietary T3 lowered (P < 0.01) plasma growth hormone. Large energy:protein diets (> 53 MJ/kg protein) increased (P < 0.01) lipogenesis, plasma growth hormone (GH) and decreased plasma insulin-like growth factor 1 (IGF-1). Also, T3 decreased plasma GH, IGF-1 in vitro lipogenesis. Ouabain inhibited a greater proportion of in vitro lipogenesis in those explants synthesizing fat at a high rate. Both dietary T3 and in vitro ouabain decrease lipogenesis, but, when combined, the effects are not cumulative.
Rosebrough
R W
RW
Nonruminant Animal Nutrition Laboratory, United States Department of Agriculture-Agricultural Research Service, Beltsville Agricultural Research Center, MD 20705.
McMurtry
J P
JP
Vasilatos-Younken
R
R
D000818:Animals; D002645:Chickens / Q000254:growth & development / Q000378:metabolism*; D004032:Diet; D004044:Dietary Proteins / Q000378:metabolism; D013006:Growth Hormone / Q000097:blood; D006980:Hyperthyroidism / Q000378:metabolism*; D050356:Lipid Metabolism; D008099:Liver / Q000378:metabolism*; D008297:Male; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism; D013963:Thyroid Hormones / Q000378:metabolism*; D014284:Triiodothyronine / Q000008:administration & dosage / Q000097:blood
D004044:Dietary Proteins; D013963:Thyroid Hormones; D014284:Triiodothyronine; D013006:Growth Hormone; D000254:Sodium-Potassium-Exchanging ATPase