Synthesis of proline and hydroxyproline in human lung (WI-38) fibroblasts

Shen, Tze-Min; Strecker, Harold J.

doi:10.1042/bj1500453

Cited by 25 publications

(6 citation statements)

References 26 publications

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“…Increased hepatic sequestration of exogenous proline, increased synthesis of proline from the physiological precursors, arginine and glutamic acid (13), and decreased proline oxidation are potentially important mechanisms. In rats with carbon tetrachloride-induced liver fibrosis (2), and recently in rats with liver fibrosis after chronic ethanol administration (28), there was enhanced conversion of glutamic acid to proline.…”

Section: Discussionmentioning

confidence: 99%

“…Elution positions of hydroxyproline and proline were verified with standard labeled amino acids. Radiochemical purity of hydroxyproline produced by liver slices and eluted by this method was confirmed by thin-layer chromatography, as described by Shen and Strecker (13). Net collagen production by liver slices was expressed as nondialyzable labeled hydroxyproline, disintegrations per minute per gram liver, formed in 6 h of incubation.…”

Section: Introductionmentioning

confidence: 99%

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Liver collagen synthesis in murine schistosomiasis.

Dunn¹,

Rojkind²,

Warren³

et al. 1977

J. Clin. Invest.

106

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A B S T R A C T Collagen synthesis was measured in liver slices obtained from mice with hepatosplenic schistosomiasis. Enlarged fibrotic livers from these mice contained 20 times more collagen than normal. This model of hepatic fibrosis results from an inflammatory granulomatous host response to Schistosoma mansoni ova in portal tracts, rather than from direct liver cell injury as with carbon tetrachloride-induced liver fibrosis. Collagen synthesis, as measured by the formation of labeled protein-bound hydroxyproline, occurred in granulomas isolated from fibrotic livers. Labeled collagen that cochromatographed with type I collagen was extracted with neutral salt solution from liver slices incubated with labeled proline. The free proline pool of the liver was doubled in infected mice; coordinately, liver slices from these animals showed maximal collagen production when the concentration of free proline in the medium was raised to 0.4 mM, the same level measured in the fibrotic livers. Under such conditions, collagen synthesis was at a rate equivalent to the formation of 5.4 nmol of protein-bound hydroxyproline per g liver in 6 h.In comparative incubations in medium containing 0.2 mM proline, fibrotic liver slices produced 16-fold more collagen than normal slices. The proline analogue, L-azetidine 2-carboxylic acid, effectively inhibited synthesis of labeled collagen by fibrotic liver slices. These studies show the synthesis of collagen in a reproducible animal model of the most prevalent form of human liver fibrosis. Definitition of the controlling factors in this system is of interest for the general problem of fibrosis produced by immunological responses.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Liver collagen synthesis in murine schistosomiasis.

Dunn¹,

Rojkind²,

Warren³

et al. 1977

J. Clin. Invest.

106

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“…In small intestine the flow is clearly from glutamate to proline and to citrulline (Windmueller & Spaeth, 1974). In fibroblasts from human lung, glutamate was better than arginine as a precursor for proline (Shen & Strecker, 1975). Since Al-pyrroline-5carboxylate dehydrogenase, A'-pyrroline-5-carboxylate reductase and arginase (in the absence of a functioning urea cycle) all catalyseunidirectional reactions, there must be additional specialized enzymes in some tissues to effect the conversion of glutamate into proline and omithine.…”

Section: Discussionmentioning

confidence: 99%

Metabolism of arginine in lactating rat mammary gland

Mezl¹,

Knox²

1977

Biochemical Journal

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Significant activities of the four enzymes needed to convert arginine into proline and glutamate (arginase, ornithine aminotransferase, pyrroline-5-carboxylate reductase and pyrroline-5-carboxylate dehydrogenase) develop co-ordinately in lactating rat mammary glands in proportion to the increased production of milk. No enzymes were detected to carry out the reactions of proline oxidation or reduction of glutamate to pyrroline-5-carboxylate. Minces of the gland converted ornithine into proline and into glutamate plus glutamine. These conversions increased during the cycle of lactation in proportion to the increased milk production and to the content of the necessary enzymes. The minced gland did not convert labelled ornithine into citrulline, confirming the absence from the gland of a functioning urea cycle, and did not convert labelled proline or glutamate into ornithine. A metabolic flow of labelled arginine to proline and glutamate in mammary gland was confirmed in intact animals with experiments during which the specific radioactivity of proline in plasma remained below that of the proline being formed from labelled arginine within the gland. It was concluded that arginase in this tissue had a metabolic role in the biosynthesis of extra proline and glutamate needed for synthesis of milk proteins.

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“…This is in contrast with the model proposed for calvarial bone in which proline entering the cell was considered to equilibrate first with the protein precursor pool (Phang et al, 1971). More recently, the importance of synthesis de novo was demonstrated for xiphoid cartilage in culture in which about 20 % of the proline incorporated into protein appeared to be synthesized from ornithine even in the presence of adequate exogenous proline (Smith & Phang, 1978), and synthesis from glutamate may be a more important pathway in some tissues (Shen & Strecker, 1975). Thus the variability in the precursor pool is probably a result of changes in the relative contribution of proline from intracellular and extracellular sources.…”

Section: Amino Acidprecursor Poolsmentioning

confidence: 99%

Metabolism of rabbit skin collagen. Differences in the apparent turnover rates of type-I- and type-III-collagen precursors determined by constant intravenous infusion of labelled amino acids

Robins¹

1979

Biochemical Journal

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Growing rabbits were infused for up to 10 h with labelled proline, tyrosine and leucine to achieve plateau conditions within body free pools, for [3H]proline infusion, blood free-proline specific radioactivity remained constant after about 1 h. For individual animals, type-I- and type-III-collagen precursors were isolated by precipitation with (NH4)2SO4 and DEAE-cellulose chromatography. Experiments where 3H- and 14C-labelled proline and tyrosine were infused concurrently for different periods of time showed that type I procollagen reached plateau specific radioactivity within 3 h and 90% of the plateau value after 2 h infusion, corresponding to a calculated apparent t 1/2 of less than 26 min. Plateau values for type I procollagen were taken as precursor amino acid pool specific radioactivities. The type-III-collagen-precursor fractions consistently showed lower rates of label incorporation and, by assuming that both type I and type III collagens are synthesized from the same amino acid pools, kinetic analysis revealed an apparent t 1/2 for the isolated type-III-collagen precursors of 3.9 h. For proline, there were large variations between animals in the ratio between the precursor pool for collagen synthesis and the skin homogenate free pool (0.31 +/- 0.13, mean +/- S.D.), so that collagen-synthesis rates based solely on total tissue free-pool values for proline are subject to large and inconsistent errors.

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Synthesis of proline and hydroxyproline in human lung (WI-38) fibroblasts

Cited by 25 publications

References 26 publications

Liver collagen synthesis in murine schistosomiasis.

Liver collagen synthesis in murine schistosomiasis.

Metabolism of arginine in lactating rat mammary gland

Metabolism of rabbit skin collagen. Differences in the apparent turnover rates of type-I- and type-III-collagen precursors determined by constant intravenous infusion of labelled amino acids

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