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Metabolism of urea in late pregnancy and the possible contribution of amino acid carbon to glucose synthesis in sheep

Published online by Cambridge University Press:  09 March 2007

J. V. Nolan  and
R. A. Leng
J. V. Nolan
Affiliation:
Department of Biochemistry and Nutrition, School of Rural Science, University of New England, Armidale, NSW 2351, Australia
R. A. Leng
Affiliation:
Department of Biochemistry and Nutrition, School of Rural Science, University of New England, Armidale, NSW 2351, Australia
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Abstract

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1. Metabolism of urea in non-pregnant and pregnant sheep (1–25 d from term) has been examined. Injections of [14C]urea were used to estimate urea entry rate, urea pool size and urea space in sheep given 1000 g of a diet of equal parts of crushed oats and chaffed lucerne hay (day a) and in the same sheep 4 d after the ration had been reduced to 250 g (day b).

2. On both experimental days (a and b), mean pool size was greater (14% on day α, 29% on day b) and urea space was greater (54% on day α, 24% on day b) in pregnant animals than in non-pregnant animals; mean plasma urea concentrations were lower (35%) in the pregnant animals on day a but were not significantly different on day b.

3. The entry rate of urea was similar in all the animals on day a, but was significantly higher (34%) in pregnant than in non-pregnant animals on day b. There was a significant decrease in urea entry rate in both pregnant (33%) and non-pregnant (86%) animals on day b.

4. The rate of excretion of urea was lower (26% on day a, 35% on day b) in pregnant animals, indicating a higher (31% on day α, 40% on day b) rate of degradation of urea in the digestive tract of pregnant as compared with non-pregnant sheep.

5. Measurements of urea entry rate have been used to calculate the upper limit of amino acid deamination in pregnant and non-pregnant sheep, and this has been used as an indication of the potential availability of amino acid carbon for glucose synthesis. It is suggested that, at a maximum, amino acids may have contributed the carbon required for 63 g/d and 52 g/d of glucose on days a and b respectively.

Type
Research Article
Information
British Journal of Nutrition , Volume 24 , Issue 4 , December 1970 , pp. 905 - 915
Copyright
Copyright © The Nutrition Society 1970

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