Lactate production in isolated perfused rat lung

Abstract

The ability of the isolated perfused rat lung to produce lactate under aerobic and hypoxic conditions has been studied. The lung has been found capable of producing lactate at a rate of 53 mumol/g dry wt per h in the presence of as great as 1 mM extracellular lactate under aerobic conditions. Essentially 100% of the lactate synthesized was derived from [U-14C]glucose. When hypoxic, the rate of lactate production doubled, but only 60% was found to be derived from [U-14C]glucose. When the perfused lung was exposed to aerobic conditions following hypoxia, it was found that lactate production did not decrease. However, lactate production from [U-14C]glucose did increase. It is concluded that lung tissue possesses a high rate of lactate production under aerobic contitions from glucose in comparison to glucose oxidation to CO2. When the lung is hypoxic, lactate production increases as a probable result of amino acid catabolism with little anaerobic energy production occurring. The effect of hypoxia was not reversed within the duration of the performed experiments.

Late Gestation Alterations in Fetal Pulmonary Lactate Metabolism in Vivo

“…Inasmuch as glucose levels are normally low in the ovine fetus, it is interesting to note that the in vitro studies in agreement with our findings (14,15) were carried out at relatively lower glucose concentrations [ l o 1 -108 mg/dL (5.6-6.0 mM)] compared to glucose levels in the discordant studies [126-180 mg/dL (7-10 mM)] (1 3, 16). Furthermore, the isolated lungs perfused with 180 mg/dL (10 mM) glucose had higher baseline rates of lactate production 1630 pg/h/g (7.0 pmol/h/g)] (1 6) than did lungs perfused with 10 1 -108 mg/dL glucose [441-468 pg of lactatejhjg (4.9-5.2 pmol/h/g)] (14,15). At lower glucose levels, lactate production may already be decreased and unresponsive to further modulation by lactate.…”

“…Studies using isolated perfused adult rat lungs as well as fetal rat type I1 pneumocytes have demonstrated an elevated rate of lactate production under conditions of significantly reduced oxygen availability (13,14,16,19). However, our results show that the usual changes in pulmonary oxygenation found during normal gestation do not influence lung lactate production.…”

“…Experiments in fresh isolated perfused adult rat lungs have demonstrated no effect of added lactate on the rate of lung lactate production, over perfusate lactate concentrations of 0-45 mg/dL (0-5 mM) (14,15). However, other studies done on isolated perfused adult rat lungs, have reported that lactate in perfusate concentrations of 18 mg/dL (2 mM) decreases lactate production by 95% (16).…”

Bioenergetic Pattern of Isolated Type II Pneumocytes in Air and during Hypoxia

“…Studies of isolated lung slices (14) and of the isolated perfused lung (15,16) (15,16) or in tissue slices (14). Differences in the experimental conditions could account for some of this difference.…”

“…At the time of harvest (48 and 96 h), the medium was removed and monolayers incubated in 3.5 ml of a dispersal medium (collagenase-trypsin-chicken serum) for [10][11][12][13][14][15] min. Cell dispersal was verified by direct observation and 6.5 ml of F12-10% FCS added to inactivate proteolytic enzymes.…”