QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Purchase Article View Shopping Cart Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Fox, R. E. Articles by Tildon, J. T. Search for Related Content PubMed PubMed Citation Articles by Fox, R. E. Articles by Tildon, J. T.

The Role of Glutamine as an Energy Source in the Developing Rat Lung^1,2,

Renee Ellen Fox^*,3, Irene B. Hopkins^*, Erwin B. Cabacungan^* and J. Tyson Tildon^*,,

^* Division of Neonatology, Department of Pediatrics Department of Biological Chemistry, University of Maryland School of Medicine, Baltimore, MD 21201

Because multiple substrates have been shown to play a role in the metabolic homeostasis of different tissues, a series of studies were initiated to examine the role of alternate substrates in the lung. In these studies, we measured rates of oxidation of glutamine, glucose, lactate and 3-hydroxybutyrate in fibroblasts isolated from d 19 fetal rat lungs by measuring the production of ¹⁴CO₂ from labeled substrates and compared them with earlier studies of isolatedType II cells. The rate of glutamine oxidation was 16.04 nmol ¹⁴CO₂·mg protein^-1·hr^-1 in the fibroblasts compared with 24.36 in Type II cells. Three-hydroxybutyrate had a rate of 10.75 in the fibroblastsand 14.9 in the Type II cells. Lactate oxidation in fibroblasts was similar to that of glutamine, with a rate of 18.49; however, in Type II cells the rate of lactate oxidation was significantly higher at 40.29. Glucose was oxidized at a rate significantly lower than the other three substrates. In the fibroblasts, that rate was 1.22 and in Type II cells it was 2.13. To examine the interactions of substrates normally found in the intracellular milieu, we measured the effect of unlabeled substrates as competitors on labeled substrate in the fibroblats, similar to our studies with Type II cells that identified multiple metabolic compartments of energy metabolism in these cell populations. Glucose, but not lactate, inhibited the oxidation of glutamine, suggesting a compartmentation of tricarboxylic acid cycle activity rather than simple dilution by glucose. Glucose and lactate had reciprocal inhibition in the Type II cells. Our data suggest at least two separate compartments in developing lung cells for substrate oxidation: one for glutamine metabolism and a second for glucose metabolism. In summary, we have documented that glutamine and other alternate substrates are oxidized preferentially over glucose for energy metabolism in the d 19 fetal rat lung.

KEY WORDS: • energy substrates • fibroblasts • glutamine • lung development • rat • Type II pneumocytes

¹ Presented as part of the Symposium: "Glutamine Nutrition and Metabolism: Bridging Clinical Medicine and Basic Science" given at the Experimental Biology '95 meeting, Atlanta, GA, on April 13, 1995. This symposium was sponsored by the American Institute of Nutrition and supported in part by Ross Laboratories. Guest editor for the symposium publication was Josef Neu, University of Florida, Gainesville, FL.

² Supported in part by the Frank C. Bressler Fund of the University of Maryland School of Medicine.

³ To whom correspondence should be addressed: Department of Pediatrics, N5W68, University of Maryland Hospital, 22 South Greene Street, Baltimore, MD 21201-1595.