Author
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Rosebrough, Robert |
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Submitted to: Life Sciences
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 10/15/1994 Publication Date: N/A Citation: N/A Interpretive Summary: Turkey meat is valued because of its high protein and low-fat content. In addition, turkeys have been genetically selected to emphasize lean tissue development. This selection is noteworthy when the breast muscle is examined. Conversely, little is known about lipid metabolism as a function of this selection process. In addition, methods are lacking to adequately determine rates of metabolism of turkey liver tissue. The lack of methods inhibits the determination of control points in metabolism that may be subject to control and manipulation through biotechnology. Tissue culture techniques were derived that allowed the use of avian liver explants (pieces of intact liver) to determine both optimum assay conditions and points in metabolic pathways that could be regulated by products of biotechnology. Unlike mammalian liver tissue, the avian liver may not respond to the hormone insulin but is more responsive to the catecholamine family of hormones. Catecholamines are of importance because of the ability of these hormones to cause a preferential change in the broiler carcass such that the end product contains less fat and more muscle. Technical Abstract: Recent reports have indicated that certain beta-adrenergic compounds may be more effective in regulating body composition and metabolism of the domestic turkey than the chicken. A study was conducted to determine sensitivity of turkey liver explants to certain purported adrenergic agonists to determine if liver metabolism was responsive to these agents. A mechanical tissue chopper was used to obtain liver explants (35-75 mg) from 2 to 3-wk-old turkeys to determine both tissue sensitivity and metabolic effects of adrenergic agents (isoproterenol. propranolol, norepinephrine and phenoxybenzamine). A previously noted catecholamine induced decrease in in vitro lipogenesis in chicken liver explants was also noted in turkey liver explants. Thus, one set of control points for in vitro regulation is under control of the cAMP system. Preincubation of slices (1 hr) with propranolol blocked the inhibition of lipogenesis caused by alpha- and alpha-adrenergic agonists (arterenol or isoproterenol) during a subsequent 1-hr incubation. Preincubation of slices with either of these agonists decreased lipogenesis even following an extensive washout. Inhibition could be overcome with propranolol, a beta-adrenergic antagonist. Results indicate that certain beta-adrenergic agents may be more potent regulators of metabolism in the domestic turkey than in the domestic chicken. |
