HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Mathias, M. M. Articles by Elliot, J. M. Search for Related Content PubMed PubMed Citation Articles by Mathias, M. M. Articles by Elliot, J. M.

Propionate Metabolism by Bovine Liver Homogenates with Particular Reference to Stress of Lactation¹

Department of Animal Science, Cornell University, Ithaca, New York

ABSTRACT

Nuclear-free liver homogenates were employed to study the rate of incorporation of specifically labeled propionate into methyl-malonate and tricarboxylic acid cycle intermediates. The liver tissue was homogenized in a hypotonic solution. The medium was supplemented with essential coenzymes and incubated for 15 min at 37 C. Reaction products were isolated by column chromatography. Liver samples were obtained by biopsy from dairy cows representing various stages of lactation and levels of milk production. Considerable variation was found among cows in their ability to metabolize propionate. The incorporation of ¹⁴C-label from propionate into metabolic intermediates beyond methylmalonate was positively correlated with liver vitamin B₁₂ concentration. This assay criterion was a reflection of methylmalonyl-CoA mutase activity; however, to what extent variations in propionyl-CoA synthetase and carboxylase and racemase enzyme activities affected the magnitude of this parameter could not be assessed. The absence of stimulation by in vitro addition of coenzyme B₁₂ was interpreted to suggest that the apoenzyme was saturated with coenzyme. A portion of the variation in ability to metabolize propionate could be accounted for by differences in certain lactation characteristics. In general, as the degree of stress of lactation increased, the ability to metabolize propionate decreased.

¹ Supported in part by a grant from Cooperative Grange League Federation Exchange, Inc. (Now Agway, Inc., Syracuse, N.T.)

² Present address: U.S. Army Medical Research and Nutrition Laboratory, Fitzsimons General Hospital, Denver, Colorado.