Protein metabolism in lung: use of isolated perfused lung to study protein degradation

Chiang, M. J.; Whitney, Philip L.; Massaro, Donald

doi:10.1152/jappl.1979.47.1.72

Cited by 18 publications

(6 citation statements)

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“…The rate obtained for lung is similar to that obtained in vivo for rats by Garlick et al (1980), but more rapid than that observed in young growing pigs (Garlick et al, 1976). Studies on perfused lungs have produced discrepant results, with rates ranging from 14%/day (Rannels et al, 1979) to 72%/day (Chiang et al, 1979) for adult rats. The extremely rapid rates for lung protein metabolism are consistent with the currently recognized role of the lung as a metabolically active organ for other substrates such as lipids and carbohydrates (Tierney, 1974;Tierney & Levy, 1976;Mason, 1976), and demonstrate the inadequacy of the traditional view of lung as an inert tissue which functions simply as a vehicle for gas exchange.…”

Section: Discussionsupporting

confidence: 69%

Rates of collagen synthesis in lung, skin and muscle obtained in vivo by a simplified method using [3H]proline

Laurent¹

1982

Biochemical Journal

112

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Methods for measurement of rates of collagen synthesis in vivo have thus far been technically difficult and often subject to quite large errors. In this paper a simplified method is described for obtaining synthesis rates of collagen and non-collagen proteins, for tissues of rabbits. This involves an intravenous injection of [3H]proline, administered with a large dose of unlabelled proline, and measurement of the specific radioactivity of proline and hydroxyproline in body tissues up to 3 h later. The specific radioactivity of [3H]proline in plasma and the tissue free pools rises rapidly to a plateau value which is maintained for at least 2 h, when the specific radioactivity of the type I collagen precursors, isolated from the skin, was similar to that of the plasma and tissue-free pool. Furthermore, over this period, the increase in the specific radioactivity of proline in collagen and non-collagen protein was linear with respect to time. These results suggest that the large dose of proline floods the precursor pools for protein synthesis, and that this effect can be maintained for quite long periods of time. Such kinetics greatly simplified the method for obtaining collagen synthesis rates in vivo, which were calculated for lung, heart, skin and skeletal muscle, and shown to be quite rapid, ranging between about 3 and 10%/day. The lung was a particularly metabolically active tissue, with synthesis rates of about 10%/day for collagen and 35%/day for total non-collagen proteins, indicating rapid turnover of both intracellular and extracellular proteins of this tissue.

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Section: Discussionsupporting

confidence: 69%

Rates of collagen synthesis in lung, skin and muscle obtained in vivo by a simplified method using [3H]proline

Laurent¹

1982

Biochemical Journal

112

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“…We think that lungs in our control group did not have more than, at most, a minimal amount of edema. The reasons for this conclusion are (a) their percent dry weight was the same after 1 h of perfusion as we previously found at the onset of perfusion (10), (b) the ratio of lung weight to body weight was the same after 1 h of perfusion as in freshly excised lungs (23), and (c) the percent dry weight (18%) of control lungs was only slightly lower than predicted for bloodless lungs (24).…”

Section: Discussionsupporting

confidence: 71%

“…The animals were anesthetized by giving pentobarbital sodium (30 mg/kg) intraperitoneally, and were killed by exsanguination while the lung was excised and placed in the perfusion chamber. The method ofperfusing and ventilating the isolated lung has been previously described in detail (10). In essence, the excised lungs were kept at 37°C, and ventilated at 40 breaths/min with warm humidified gas (95% 02:5% C02) at a tidal volume based on the rat's body weight (11).…”

Section: Methodsmentioning

confidence: 99%

Regulation of secretion in Clara cells: studies using the isolated perfused rat lung.

Massaro¹,

Fischman²,

Chiang³

et al. 1981

J. Clin. Invest.

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A B S T R A C T Previous studies from our laboratory indicated that both beta-adrenergic and cholinergic agents stimulate in vivo secretion by rat bronchiolar Clara cells. Those studies also provided support for an in-series beta-adrenergic-cholinergic stimulation of secretion. To further explore the regulation of secretion in Clara cells, and to do it in the absence of systemic influences, we have used the isolated ventilated perfused rat lung. We have again used morphometry and electron microscopy to assess secretion by measuring the volume density (fraction of cell volume) of the secretory granules of bronchiolar Clara cells. We found that in the isolated perfused lung, as in the intact animal, isoproterenol stimulated secretion in Clara cells and that this effect was blocked by the betaadrenergic antagonist propranolol. Pilocarpine, unlike its action in the intact animal, did not stimulate secretion in the isolated lung; rather it inhibited the secretory effect of isoproterenol. Increased tidal-volume ventilation stimulated secretion; propranolol did not block this effect. Analogs of cyclic (c)AMP and of cGMP also stimulated secretion by Clara cells. These findings indicate that there are at least two mechanisms by which Clara cells can be stimulated to secrete. One seems to be beta-adrenergic-cAMP mediated but the triggering event is unknown. The other is initiated by increased tidal volume and cGMP may be involved in the intracellular mediation ofthis stimulatory event. Finally, we found evidence of beta-adrenergic

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“…The isolated perfused lung system was the same as previously described in detail (9). Briefly, the excised lungs were kept at 37°C, and ventilated at 40 breaths-min-' with warm humidified gas (95% 02:5% CO2) at a tidal volume (or two times tidal volume) based on the rats body weight (10).…”

Section: Methodsmentioning

confidence: 99%

Studies on the Regulation of Secretion in Clara Cells with Evidence for Chemical Nonautonomic Mediation of the Secretory Response to Increased Ventilation in Rat Lungs

Massaro¹,

Amado²,

Clerch³

et al. 1982

J. Clin. Invest.

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A B S T R A C T Using electron microscopy and morphometric methods to assess secretion, we previously found that two times tidal volume ventilation of isolated perfused rat lung stimulates secretion by bronchiolar Clara cells; this effect is not prevented by #-adrenergic blockade (J. Clin. Invest. 1981. 67: 345-351.). In this study we used the isolated perfused rat lung and the anesthetized mechanically ventilated rat, to further study the mechanism by which large tidal volumes stimulate secretion by Clara cells. With the perfused lung we found (a) a-adrenergic inhibition did not block the secretory effect of ventilation at two times normal tidal volume; (b) indomethacin completely blocked the secretory action of two times tidal volume ventilation; (c) medium previously used to perfuse lungs ventilated at two times tidal volume, but not medium previously used to ventilate lungs at normal tidal volume, stimulated secretion by Clara cells when used to perfuse fresh lungs ventilated at tidal volume; (d) addition of prostacyclin to the fresh perfusate increased secretion by Clara cells of lungs ventilated at normal tidal volume. In anesthetized mechanically ventilated rats, sighs stimulated secretion by Clara cells; this increased secretion was inhibited by indomethacin but not by cholinergic blockade (bilateral vagotomy

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Protein metabolism in lung: use of isolated perfused lung to study protein degradation

Cited by 18 publications

References 0 publications

Rates of collagen synthesis in lung, skin and muscle obtained in vivo by a simplified method using [3H]proline

Rates of collagen synthesis in lung, skin and muscle obtained in vivo by a simplified method using [3H]proline

Regulation of secretion in Clara cells: studies using the isolated perfused rat lung.

Studies on the Regulation of Secretion in Clara Cells with Evidence for Chemical Nonautonomic Mediation of the Secretory Response to Increased Ventilation in Rat Lungs

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