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Agricultural Research, Science and Education Administration, U.S. Department of Agriculture, ,4 Clay Center, NE 68933
Crossbred steers (seven to nine per treatment) fed a pelleted alfalfa hay diet were biopsied (preinfusion) to obtain subcutaneous adipose tissue (SAT). Five days later a continuous intravenous infusion was begun of either 0.9% NaCl, glucose (2.75 moles/day), DL-lactate (5.5 moles/day of L-lactate), propionate (5.5 moles/day) or acetate (8.25 moles/day); after infusion for 14 days, a second biopsy sample of SAT was obtained. Glucose and DL-lactate infusion increased acetyl-CoA carboxylase activity about 12-fold compared to preinfusion activity of 5.3 ± 4.2 nmoles/minute/g of wet weight. Glucose infusion induced activities of fatty acid synthetase (2.6 fold) and NADP+-malate dehydrogenase (7-fold) relative to preinfusion activities of 26.8 ± 5.2 and 30.3 ± 15.5 nmoles/minute/g of wet weight, respectively. Glucose, DL-lactate and propionate infusion increased NADP-isocitrate dehydrogenase activity 2030% compared to preinfusion activity. Activity of NAD-malate dehydrogenase was not altered by any infusion treatment (P > 0.05). Activity of ATP-citrate lyase was decreased 48% by lactate infusion. Glucose, lactate and propionate infusion increased the rates of lactate and glucose incorporation into fatty acids in SAT incubated in vitro three to fourfold over preinfusion incorporation rates. Increased availability of glucose or gluconeogenic precursors may be responsible for induction of lipogenesis in steers fed high concentrate diets.
KEY WORDS: glucose propionate DL-lactate acetate lipogenic enzymes bovine
1 The cooperation of the Nebraska Agricultural Experiment Station, University of Nebraska, Lincoln, is acknowledged.
2 Research chemist, Roman L. Hruska U.S. Meat Animal Research Center, Agricultural Research, Science and Education Administration.
3 Present address: Agriculture Dept., Berry College, Mt. Berry, GA 30149.
4 Mention of a trade name, proprietary product or vendor does not constitute a guarantee or warranty by the U.S. Department of Agriculture and does not imply its approval to the exclusion of the other products or vendors that may be suitable.
Manuscript received 15 April 1980.
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