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 Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Raggi, F. Articles by Kronfeld, D. S. Search for Related Content PubMed Articles by Raggi, F. Articles by Kronfeld, D. S.

Mammary Glucokinase and Dehydrogenase Activities in Normal and Spontaneously Ketotic Dairy Cows

Department of Animal Biology, School of Veterinary Medicine, University of Pennsylvania, Kennett Square

ABSTRACT

Some of the known metabolic changes in spontaneously ketotic cows could be explained by either a glucose shortage in the mammary gland or by a shortage of nicotinamide adenine nucleotide coenzymes. These changes include decreases in glucose oxidation in the pentose cycle and the citric acid cycle (9), the decrease in fatty acid synthesis from acetate (4), and perhaps the increase in mammary ketogenesis from acetate (3). A primary decrease in glucose availability in mammary cells could lead to shortages of 2-glycerophosphate, NADPH, and oxalacetate, and therefore to decreased disposal of acetyl-CoA in the citric acid cycle and in lipogenesis (1). This would leave more acetyl-CoA available for ketogenesis.

The mammary arterio-venous difference of glucose is about 10 mg/100 ml, both in normal and spontaneously ketotic cows (8). Provided there is no decrease in blood flow rate during spontaneous ketosis, the next possible step which could be impaired, and so lead in effect to an intracellular glucose shortage, is the glucokinase reaction, i.e., the phosphorylation of glucose by the enzyme hexokinase (Figure 1).