Faculty Collaboration Database

Developmentally induced changes in rat lung malic enzyme activities. Exp Lung Res 2000;26(7):509-19

Date

11/15/2000

Pubmed ID

11076309

DOI

10.1080/019021400750048063

Scopus ID

2-s2.0-0033792806 (requires institutional sign-in at Scopus site)   1 Citation

Abstract

To determine lung malic enzyme activity at varying stages of development, both cytosolic and mitochondrial enzyme activities were assayed in rat lungs at various stages from day 16 of fetal life to 2 months of postnatal life by measuring the production of 14CO2 from 14C-malate. Malic enzyme activities were significantly higher in the mitochondrial than in the cytosolic fractions at all ages studied. The mitochondrial malic enzyme activity was significantly higher in canalicular stage (days 19-20) stage of lung development when compared to the glandular stage (days 16-18). The mitochondrial fraction at day 19 exhibited biphasic kinetics: high affinity, Km = 0.45 mmol, Vmax = 10.04 nmol/mg protein/min; and low affinity, Km = 5.48 mmol, Vmax = 56.83 nmol/mg protein/min. The cytosolic malic enzyme activity of all fetal stages (saccular stage [days 16-18], canalicular stage [days 19-20], and glandular stage [days 21-22] were significantly higher when compared to postnatal levels (postnatal days 1-10, adult). In contrast to the mitochondrial fraction, at day 19, the cytosolic fraction showed a single Km of 0.23 mmol, Vmax = 12.32 nmol/mg protein/min. The increased mitochondrial malic enzyme activity during late gestation would suggest that, as we have previously demonstrated, anaplerotic substrates other than glucose, may provide a significant energy source in fetal lung. The increased cytosolic activity in the prenatal phases would suggest that the NADPH provided from malic enzyme is an important contributor to de novo fatty acid synthesis, leading to surfactant synthesis, critical to normal lung development in late gestation.

Author List

Cabacungan ET, Nhamburo PT, Hopkins IB, Fox RE

Author

Erwin Cabacungan MD Associate Professor in the Pediatrics department at Medical College of Wisconsin

MESH terms used to index this publication - Major topics in bold

Age Factors
Animals
Animals, Suckling
Carbon Dioxide
Carbon Radioisotopes
Cytosol
Female
Fetus
Kinetics
Lung
Malate Dehydrogenase
Male
Mitochondria
Models, Animal
Rats
Rats, Sprague-Dawley