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Journal of Dairy Science Vol. 68 No. 10 2550-2557
© 1985 by American Dairy Science Association ®
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Roles of Lactate and Its Interactions with Acetate in Maintenance and Biosynthesis in Bovine Mammary Tissue1

N. E. Forsberg2, R. L. Baldwin and N. E. Smith3

Department of Animal Science, University of California, Davis 95616

ABSTRACT

Mammary gland tissue slices from three lactating Holstein cows were incubated in Krebs-Ringer bicarbonate-based media with varying concentrations of lactate and other substrates. Conversions of 1- and 2-carbon-14 of lactate to carbon dioxide, fatty acids, citrate, glyceride glycerol, and lactose were determined.

Effects of acetate, glucose, beta-hydroxybutyrate, stearate, and pyruvate on lactate metabolism were evaluated. Oxidation of lactate increased asymptotically with lactate concentration. Low acetate concentration stimulated oxidation of carbon 2 of lactate slightly while higher acetate availability inhibited lactate oxidation. Conversion of lactate to fatty acids increased linearly with lactate concentration. This conversion of lactate was inhibited strongly by acetate. Significant conversion of carbon 2 of lactate to glyceride-glycerol but not lactose was detected.

Bovine mammary glands have the capacity of utilize sizeable quantities of lactate for oxidation and lipogenesis. Both phenomena are highly dependent on availability of acetate. Pyruvate dehydrogenase and citrate lyase could represent important regulatory sites in vivo for determination of tissue preference for acetate over lactate. Results indicate factors other than an inactive malate transhydrogenation cycle likely limit glucose conversion to fatty acids.

FOOTNOTES

1 From Ph.D. thesis of N. E. Forsberg.

2 Department of Animal Science, Oregon State University, Corvallis 97331.

3 Ralston Purina, Checkerboard Square, St. Louis, MO.






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Copyright © 1985 by the American Dairy Science Association ®.