Uptake and metabolism of tryptophan by the isolated perfused guinea-pig mammary gland

Mepham, Ben; Peters, A. R.; Davis, Stephen R.

doi:10.1042/bj1580659

Cited by 6 publications

(4 citation statements)

References 10 publications

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“…The 'predicted rate of protein synthesis', calculated from the rates of uptake by the perfused gland of the five essential amino acids, methionine, tyrosine, phenylalanine, histidine and tryptophan (see Mepham et al 1976), was used to assess any effect of cortisol administration on essential amino-acid uptake and milk protein synthesis.…”

Section: Corticosteroid Concentrations In Vivomentioning

confidence: 99%

Effects of Exogenous Cortisol on the Uptake of Corticosteroids by the Isolated Perfused Guinea-Pig Mammary Gland

Peters¹,

Mepham²

1979

Journal of Endocrinology

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Assay of corticosteroids in the plasma of guinea-pigs showed that concentrations were higher in lactating than in non-lactating and male animals. In five isolated perfused mammary gland experiments in which corticosteroids were at concentrations of 1,3--3,0 microgram/ml in the perfusate, equivalent to concentrations during lactation, the mean (+/- S.E.M.) uptake by the mammary gland was 900 +/- 210 ng g-1 h-1. In five experiments in which the concentrations of corticosteroid in the perfusate were 190--580 ng/ml, the uptake by the mammary gland was significantly lower (316 +/- 73 ng g-1 h-1; P less than 0.05). For the ten experiments there was a significant correlation between the concentration of corticosteroid in the perfusate and uptake by the mammary gland (P less than 0.05). No convincing evidence for a galactopoietic role of corticosteroids in the guinea-pig was obtained, although administration of cortisol signficantly stimulated the uptake of glutamine by the perfused gland.

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Section: Corticosteroid Concentrations In Vivomentioning

confidence: 99%

Effects of Exogenous Cortisol on the Uptake of Corticosteroids by the Isolated Perfused Guinea-Pig Mammary Gland

Peters¹,

Mepham²

1979

Journal of Endocrinology

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“…There are a variety of dietary, drug, and disease factors that reduce the conversion of tryptophan to niacin (McCormick, 1988), including a decreased concentration of available free tryptophan. Tryptophan is included in the category of essential amino acids that may limit milk-protein synthesis (Mepham et al, 1976). This may be an important feature that differentiates the niacin production between fasting females and weaned pups.…”

Section: Discussionmentioning

confidence: 99%

Water-soluble vitamin homeostasis in fasting northern elephant seals (Mirounga angustirostris) measured by metabolomics analysis and standard methods

Boaz

Champagne

Fowler

et al. 2012

Comparative Biochemistry and Physiology Part A: Molecular &

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Despite the importance of water-soluble vitamins to metabolism, there is limited knowledge of their serum availability in fasting wildlife. We evaluated changes in water-soluble vitamins in northern elephant seals, a species with an exceptional ability to withstand nutrient deprivation. We used a metabolomics approach to measure vitamins and associated metabolites under extended natural fasts for up to seven weeks in free-ranging lactating or developing seals. Water-soluble vitamins were not detected with this metabolomics platform, but could be measured with standard assays. Concentrations of measured vitamins varied independently, but all were maintained at detectable levels over extended fasts, suggesting that defense of vitamin levels is a component of fasting adaptation in the seals. Metabolomics was not ideal for generating complete vitamin profiles in this species, but gave novel insights into vitamin metabolism by detecting key related metabolites. For example, niacin level reductions in lactating females were associated with significant reductions in precursors suggesting downregulation of the niacin synthetic pathway. The ability to detect individual vitamins using metabolomics may be impacted by the large number of novel compounds detected. Modifications to the analysis platforms and compound detection algorithms used in this study may be required for improving water-soluble vitamin detection in this and other novel wildlife systems.

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“…Previous work in this laboratory has shown that the isolated perfused guinea-pig mammary gland absorbs essential amino acids from the perfusate in amounts related to the output of these amino acids in milk protein (Davis & Mepham, 1974). We have suggested that essential amino acids belong to one of two categories, group 1, consisting of methionine, tyrosine, phenylalanine, histidine and tryptophan, the uptakes of which agree very closely with their outputs in milk protein, and group 2, consisting of threonine, valine, isoleucine, leucine, lysine and arginine, which are absorbed in excess of their requirement for protein synthesis (Davis & Mepham, 1976;Mepham, Peters & Davis, 19766;Peters, Alexandrov & Mepham, 1979).…”

mentioning

confidence: 99%

“…In contrast, the group 1 amino acids are catabolized to a lesser, and often negligible, extent, e.g. methionine (Verbeke, Simeonov & Peeters, 1967), tryptophan (Mepham et al 19766), histidine and phenylalanine (Davis & Mepham, 1976).…”

mentioning

confidence: 99%

Effects of restriction of amino acid supply to the isolated perfused guinea-pig mammary gland

Mepham

Peters

1979

Journal of Dairy Research

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SUMMARYWhen individual essential amino acids were omitted for periods of 40–100 min from the infusate substrate solution in isolated perfused guinea-pig mammary gland experiments, uptake of methionine, tyrosine, phenylalanine, histidine and tryptophan (group 1) was significantly depressed by a mean of 49·8%, whereas the remaining essential amino acids (group 2) showed no significant decrease in uptake. During depletion periods oxidation of [14C\amino acids was increased. The possible significance of the differences in absorption between the 2 groups of amino acids is discussed.

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Uptake and metabolism of tryptophan by the isolated perfused guinea-pig mammary gland

Cited by 6 publications

References 10 publications

Effects of Exogenous Cortisol on the Uptake of Corticosteroids by the Isolated Perfused Guinea-Pig Mammary Gland

Effects of Exogenous Cortisol on the Uptake of Corticosteroids by the Isolated Perfused Guinea-Pig Mammary Gland

Water-soluble vitamin homeostasis in fasting northern elephant seals (Mirounga angustirostris) measured by metabolomics analysis and standard methods

Effects of restriction of amino acid supply to the isolated perfused guinea-pig mammary gland

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