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. 1965 Sep;96(3):607–615. doi: 10.1042/bj0960607

Estimation of the pentose cycle in the perfused cow's udder

Harland G Wood 1, Georges J Peeters 1, Roger Verbeke 1, Monique Lauryssens 1, Birgit Jacobson 1
PMCID: PMC1207194  PMID: 5862402

Abstract

1. The distributions of 14C have been compared in the glucose and galactose moieties of lactose obtained from cows' udders perfused with blood containing [1-14C]-, [2-14C]- and [6-14C]-glucose. The 14C of the glucose moiety was found in the same position as that of the administered glucose, but in the galactose moiety the 14C from [2-14C]glucose was extensively randomized into positions 1 and 3. It is concluded that the glucose moiety arose from free glucose and the galactose moiety from hexose phosphate intermediates and that the latter reflected the randomization occurring through reactions of the pentose cycle. 2. The proportion of the glucose metabolized via the pentose cycle for those cells making lactose was estimated from the distribution of 14C in the galactose moiety and found to be about 23% in one experiment and 30% in another experiment. 3. The yield and distribution of 14C were determined in the glycerol of fat from the tissue in experiments with [2-14C]- and [6-14C]-glucose. There was a greater randomization of 14C in the glycerol than in C-1, C-2 and C-3 of the galactose moiety of lactose. The ratio of the yield of 14C in the glycerol from [2-14C]glucose to that of [6-14C]glucose was very low and from this ratio it was calculated that less than 10% of the glucose was metabolized by the Embden–Meyerhof pathway and approx. 60–70% was converted into lactose. 4. [6-14C]Glucose and [6-3H]glucose were used to determine whether the 3H at the C-6 position remained stable during its conversion into glyceride of fat from the tissue. Twenty-seven per cent of the 3H was labilized during this conversion. Therefore it was not possible to use [2-14C]glucose and [6-3H]glucose in a single experiment to measure the relative conversion of the C-2 and C-6 positions of glucose to glycerol.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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