Diethyl pyrocarbonate (DEPC) inhibits CO2 chemosensitivity in Helix aspersa

Central CO₂ chemoreceptors in poikilothermic vertebrates may not regulate ventilation at a particular pH setpoint; central chemoreceptor responses may more accurately reflect the relative charge state (alpha) of the imidazole of histidine. We have tested the alphastat hypothesis in the terrestrial, air breathing, pulmonate snail, Helix aspersa, by chemically modifying histidine residues in the central CO₂ chemoreceptor area of this animal using diethyl pyrocarbonate (DEPC). After focal application of 20 mM DEPC to the central CO₂ chemoreceptor region, the pneumostome, a respiratory, CO₂ responsive organ in the snail, no longer responded to hypercapnic, acidotic stimulation of the central chemoreceptor area. However, pneumostomal responses to hypoxic stimulation of the pneumostome and to focal stimulation of the central chemoreceptor area with sodium nitroprusside, a respiratory stimulant in H. aspersa, remained intact after DEPC treatment. Furthermore, DEPC treatment of the central chemoreceptor area blocked pneumostomal responses to ammonia pre-pulse treatment, which changes intracellular pH, while extracellular pH is held constant. These results resemble mammalian responses to DEPC treatment and indicate that central chemoreceptor responses in H. aspersa may originate from changes in the alpha of intracellular histidine residues.     

Acid-base balance and the control of respiration during anaxic and anoxic-hypercapnic gas breathing in turtles

We studied the ventilatory and blood acid-base response of turtles to 6 of breathing eithe 100% N₂(anoxic) or 95% N₂-5% CO₂ (anoxic-hypercapnic). In both groups, minute ventilation (V̇E) increased promptly with anoxia, with peak ventilation occurring between 1 and 3 h. V̇E then decreased but was still significantly above control at 6h. The increase in V̇E resulted from increases in both respiratory frequency (f) and tidal volume (VT) but after ventilation peaked, f declined to control while VT remained elevated. We observed no significant differences in V̇E between the two groups in spite of significantly lower arterial pH and higher arterial P_CO2 in the anoxic-hypercapnic turtles. During normoxic recovery, V̇E quickly increased to the peak anoxic values due primarily to a greatly increased f. In both groups, plasma [lactate⁻] increased during anoxia. Plasma cation concentrations also increased, partially compensating for the elevated blood lactate. We conclude that the anoxic hyperventilation did not depend on arterial pH and central chemoreceptor control but rather on peripheral hypoxic chemoreceptor control. We believe that the decline in V̇E during prolonged anoxic breathing results from a metabolic arrest response and/or a depression in central nervous function.     

The effect of pH on 86Rubidium efflux from pancreatic islet cells

The influence of pH on the K⁺ permeability of pancreatic islet cells was investigated by measuring ⁸⁶Rb⁺ fluxes in isolated rat islets perifused or incubated in the absence of glucose. Acidification of the medium (to pH 6.5), by decreasing the concentration of HCO^?₃ or by increasing pCO₂ at constant HCO^?₃ reversibly reduced the rate of ⁸⁶Rb⁺ efflux from perifused islets. Alkalinization of the medium (to pH 7.8), by decreasing the pCO₂, reversibly increased ⁸⁶Rb⁺ efflux. Similar changes were recorded upon alteration of the pH in a bicarbonate-free, Hepesbuffered medium with or without calcium. Alteration of the CO₂ level at constant external pH — in order to modify internal pH — produced only a small and transient increase in efflux rate when CO₂ was lowered, and a decrease in efflux rate when CO₂ was raised. NH₄Cl reversibly augmented ⁸⁶Rb⁺ efflux in the presence and in the absence of HCO^?₃. At low pH (6.5), ⁸⁶Rb⁺ uptake by islet cells was reduced after 10 min (25%) and 30 min (11%), but not after 60 min, of incubation; it was not significantly affected by high pH (7.8). Calcium uptake and insulin release were reduced at low pH and increased at high pH.These results show that the K⁺ permeability of islet cells is affected by changes in extracellular but not in intracellular pH. They suggest that the endogenous production of protons that accompanies glucose stimulation of islet cells is not the mediator of the decrease in K⁺ permeability induced by the sugar.     

Integration of bronchomotor and ventilatory responses to chemoreceptor stimulation in developing sheep

We analyzed the changes induced by central chemoreceptor stimulation on the lung resistances and phrenic neurogram of anesthetized newborn (3–6 days, n=9) and 9 week old lambs (n=3). Starting from hypocapneic apnea, 5% CO₂ inhalation evoked a reversible increase in total lung resistance in both newborn and 9 week old lambs (median=112%). The resistance increase preceded phrenic breathing and was greater for the peripheral (233%) than for the central airways (57%), independent of age. Increases in lung and airway resistance caused by CO₂ were reversed totally by atropine and only partially by apnea-producing doses of fentanyl. Our results demonstrate that parasympathetic outflow to the sheep airways is already driven by central chemoreceptor inputs during the newborn period. Even at this early age, bronchomotor responses to central chemoreceptor stimulation are more prominent in the peripheral than in the central airways and exhibit a lower threshold for activation and less sensitivity to opioid inhibition than phrenic responses.     

Acidosis tubular renal distal autosómica dominante en dos pacientes pediátricos con mutaciones en el gen SLC4A1. ¿La prueba de la pCO2 urinaria máxima puede ser normal?

Primary distal renal tubular acidosis (dRTA) is a rare tubulopathy characterized by the presence of hyperchloremic metabolic acidosis. It is caused by the existence of a defect in the function of the H⁺-ATPase located on the luminal side of the α-intercalated cells or the Cl⁻ HCO₃⁻ (AE1) anion exchanger located on the basolateral side. Patients do not acidify the urine after acid overload (NH₄Cl) or after stimulating H⁺ secretion by obtaining a high intratubular concentration of an anion such as chlorine (pH is measured) or HCO₃⁻ (urinary pCO₂ is measured). We present a family with autosomal dominant dRTA produced by a heterozygous mutation in the SLC4A1 gene in which the two pediatric members showed a test of normal maximum urinary pCO₂. Our hypothesis is that since the H⁺-ATPase is intact, at least initially, the stimulation induced by intratubular electronegativity to secrete H⁺ could be effective, which would allow the maximum urinary pCO₂ to be paradoxically normal, which could explain the onset, moderate presentation of symptoms and late diagnosis in patients with this mutation. This is the first documented case of a dominant dRTA in Mexico.     

Buffering characteristics of eel blood at the extreme conditions in the swimbladder

CO₂ binding in whole blood and true plasma of the eel was estimated by measuring CO₂ content and pH in blood aliquots equilibrated with various P_CO2 values over a wide range expected to occur in the swimbladder. Bicarbonate concentration, [HCO₃⁻], was calculated using the CO₂ solubility coefficient, which was measured to average 50 μmol·L⁻¹·Torr⁻¹ (20°C). Buffer lines of non-bicarbonate buffers were obtained in plots of [HCPO₃⁻] against pH, and non-bicarbonate buffer values, β_NB, were obtained by curve. fitting.In the pH range 6.6–8.2, the buffer line for oxygenated whole blood was sigmoid, while that for deoxygenated blood increased its slope monotonously with increasing pH. The β_NB for oxygenated blood displayed a maximum of about 8.6 mmol·L⁻¹pH⁻¹ at pH = 7.4 and dropped down to below 1 mmol·L⁻¹·pH⁻¹ at higher and lower pH. Similar shapes of the buffer lines were obtaned in true plasma; the [HCO₃⁻] levels and β_NB values were, however, somewhat higher than in whole blood.These data are useful fo assess the back-diffusion of CO₂ and HCO₃⁻ in the rete mirabile of the fish swimbladder and to estimate the effects CO₂ back-diffusion exerts on the counter-current enhancement of O₂ in the rete.     

Tachykinin antagonists in carotid body responses to hypoxia and subtance P in the rat

In the present study, we tested the hypothesis that substance P (SP) is an excitatory peptide to the rat carotid body and plays an important role in chemosensory excitation by hypoxia. Chemosensory discharge was recorded from the cut carotid sinus nerve in 19 anaesthetized, paralyzed and mechanically ventilated rats. Intracarotid admininstration of SP augmented the chemoreceptor activity in a dose-dependent manner. Maximal excitation was seen with 10 nmol SP. Carotid body stimulation by SP was independent of its effects on arterial blood pressure. The effect of SP antagonist, D-Pro²-D-Trp^7.9-SP (DPDT-SP) or Spantide, on chemoreceptor responses to SP and hypoxia was examined in 12 rats. Close carotid body administration of either at doses of 40 μg·kg⁻¹·min⁻¹ elicited an augmentation followed by a progressive depression of baseline carotid body activity. SP antagonists significantly reduced peptide-induced carotid body stimulation and also markedly attenuated the chemoreceptor response to hypoxia. Systemic administration of sodium bicarbonate stimulated the carotid bodies, presumably by releasing CO₂, and the bicarbonate-induced chemoreceptor stimulation was not affected by SP antagonists. From the results the conclude that in rats (a) SP stimulates the carotid bodies independently of its effects on arterial blood pressure, and (b) SP is associated with the chemosensory stimulation by hypoxia but not with other excitatory stimuli.     

Ammonia acquisition in enteric bacteria: Physiological role of the ammonium/methylammonium transport B (AmtB) protein

Homologues of the amtB gene of enteric bacteria exist in all three domains of life. Although their products are required for transport of the ammonium analogue methylammonium in washed cells, only in Saccharomyces cerevisiae have they been shown to be necessary for growth at low NH₄⁺ concentrations. We now demonstrate that an amtB strain of Escherichia coli also grows slowly at low NH₄⁺ concentrations in batch culture, but only at pH values below 7. In addition, we find that the growth defect of an S. cerevisiae triple-mutant strain lacking the function of three homologues of the ammonium/methylammonium transport B (AmtB) protein [called methylammonium/ammonium permeases (MEP)] that was observed at pH 6.1 is relieved at pH 7.1. These results provide direct evidence that AmtB participates in acquisition of NH₄⁺/NH₃ in bacteria as well as eucarya. Because NH₃ is the species limiting at low pH for a given total concentration of NH₄⁺ + NH₃, results with both organisms indicate that AmtB/MEP proteins function in acquisition of the uncharged form. We confirmed that accumulation of [¹⁴C]methylammonium depends on its conversion to γ-N-methylglutamine, an energy-requiring reaction catalyzed by glutamine synthetase, and found that at pH 7, constitutive expression of AmtB did not relieve the growth defects of a mutant strain of Salmonella typhimurium that appears to require a high internal concentration of NH₄⁺/NH₃. Hence, contrary to previous views, we propose that AmtB/MEP proteins increase the rate of equilibration of the uncharged species, NH₃, across the cytoplasmic membrane rather than actively transporting—that is, concentrating—the charged species, NH₄⁺.     

Effects of central and peripheral chemoreceptor stimulation on ventilation in the marine toad, Bufo marinus

The contributions of central and peripheral chemoreceptors to respiratory control in lightly anesthetized Bufo marinus, were assessed by measuring the ventilatory responses to unidirectional ventilation (UDV) of the lungs at several concentrations of CO2 or O2, during intracranial perfusion (ICP) with hypercapnic acidic (5% CO2, pH 7.2) or hypocapnic alkaline (0% CO2, pH 8.3) mock CSF solutions. Peripheral chemoreceptor stimulation alone (hypoxia or hypercapnia during ICP with hypocapnic alkaline CSF) significantly increased breathing frequency and amplitude. ICP with hypercapnic acidic CSF further stimulated ventilation, primarily by significantly increasing the number of breaths/bout of breathing and decreasing the non-ventilatory time at all levels of peripheral ventilatory drive. When peripheral and central chemoreceptor stimulation was low toads were apneic. Stimulation of either central or peripheral chemoreceptors was sufficient to reinitiate breathing. Responses to ICP were greatest when perfusion was directed to the ventral medullary surface (VMS). These results suggest that the initiation of breathing and overall levels of breathing are functions of the combined afferent input from peripheral chemoreceptors and central CO2/pH sensitive chemoreceptors, located near the VMS. Stimulation of central chemoreceptors, however, produced longer duration bouts of rhythmic breathing than did peripheral chemoreceptor stimulation.     

The ventilatory and metabolic response to hypercapnia in newborn mammalian species

Conscious newborns of 12 species from 4 mammalian orders, ranging in body mass (M) from 1 g (mouse) to 5 kg (deer), were studied during air and during 5% CO₂ breathing. The interspecies relationship between oxygen consumption (V̇_O2) and M was the same in air and hypercapnia, in both cases V̇_O2 ∝ M^0.90; on average, hypercapnic V̇_O2 was 101% of the air value. In 5% CO₂, ventilation (V̇e) increased in all newborns, mostly because of the increase in tidal volume (178%), whereas breathing rates averaged 98% of the air values. The hyperpnea during CO₂ was slightly greater in the larger newborns. Body temperature was not altered by CO₂ breathing. We conclude that the average respiratory response of the newborn to moderate hypercapnia is a hyperventilation different from that of the neonatal mammal in acute hypoxia (Mortola et al., Respir. Physiol. 78: 31–43, 1989). In fact, hypercapnic hyperventilation resulted only from the hyperpnea, with no hypometabolic contribution, and the hyperpnea reflected the increase in tidal volume, with no change in rate. It is also concluded that the neonatal hypometabolic response is specific to hypoxia, and not an undifferentiated response to chemoreceptors stimulation.     

Acute respiratory failure and obesity with normal ventilatory response to carbon dioxide and absent hypoxic ventilatory drive

We measured hypoxic and hypercapnic ventilatory drive in a 64 year old woman with acute respiratory failure, congestive heart failure and obesity when she was in remission. She had a ventilatory response to carbon dioxide (CO₂) comparable to that in six obese women without hypoventilation but no ventilatory response to hypoxia or to vital capacity breaths of 15 per cent CO₂ in N₂- Following weight loss, her ventilatory response to CO₂ increased but hypoxic ventilatory drive remained absent. These findings indicate that attenuation of hypoxic ventilatory drive caused by loss of peripheral chemoreceptor function can be a predisposing factor in the development of acute respiratory failure associated with obesity.     

NMR study of chloride ion interactions with thylakoid membranes

The role of Cl^- in photosynthetic O₂ evolution has been investigated by observing the ³⁵Cl NMR linewidth under a variety of conditions in aqueous suspensions of chloroplasts, primarily for the halophytes Avicennia germinans, Avicennia marina, and Aster tripolium but also for spinach. The line broadening shows there is weak, ionic binding of Cl^- to thylakoids, the bound Cl^- exchanging rapidly (>>10⁴ sec^-1) with free Cl^- in solution. The binding is necessary for O₂ evolution to occur. Michaelis-Menten constants obtained from the Cl^- dependence of the O₂ evolution rate are ≈15-70 mM for the halophytes compared with 0.6 mM for spinach (0.5 mM with Br^-). There appear to be two types of Cl^- binding sites in halophytes, of which the stronger is the activator, at lower [Cl^-], of O₂ evolution. The ³⁵Cl line broadening includes a nonspecific interaction, which becomes apparent at high Cl^- concentrations (≥0.5 M).     

Effect of Sulfate Ions on Galvanized Post-Tensioned Steel Corrosion in Alkaline Solutions and the Interaction with Other Ions

Zinc protection of galvanized steel is initially dissolved in alkaline solutions. However, a passive layer is formed over time which protects the steel from corrosion. The behavior of galvanized steel exposed to strong alkaline solutions (pH values of 12.7) with a fixed concentration of sulfate ions of 0.04 M is studied here. Electrochemical measurement techniques such as corrosion potential, linear polarization resistance and electrochemical impedance spectroscopy are used. Synergistic effects of sulfate ions are also studied together with other anions such as chloride Cl⁻ or bicarbonate ion HCO₃⁻ and with other cations such as calcium Ca²⁺, ammonium NH₄⁺ and magnesium Mg²⁺. The presence of sulfate ions can also depassivate the steel, leading to a corrosion current density of 0.3 µA/cm² at the end of the test. The presence of other ions in the solution increases this effect. The increase in corrosion current density caused by cations and anions corresponds to the following orders (greater to lesser influence): NH₄⁺ > Ca²⁺ > Mg²⁺ and HCO₃⁻ > Cl⁻ > SO₄²⁻.     

HIV protease inhibitors elicit volume-sensitive Cl current in cardiac myocytes via mitochondrial ROS

HIV protease inhibitors (HIV PI) reduce morbidity and mortality of HIV infection but cause multiple untoward effects. Because certain HIV PI evoke production of reactive oxygen species (ROS) and volume-sensitive Cl⁻ current (I_Cl,swell) is activated by ROS, we tested whether HIV PI stimulate I_Cl,swell in ventricular myocytes. Ritonavir and lopinavir elicited outwardly rectifying Cl⁻ currents under isosmotic conditions that were abolished by the selective I_Cl,swell-blocker DCPIB. In contrast, amprenavir, nelfinavir, and raltegravir, an integrase inhibitor, did not modulate I_Cl,swell acutely. Ritonavir also reduced action potential duration, but amprenavir did not. I_Cl,swell activation was attributed to ROS because ebselen, an H₂O₂ scavenger, suppressed ritonavir- and lopinavir-induced I_Cl,swell. Major ROS sources in cardiomyocytes are sarcolemmal NADPH oxidase and mitochondria. The specific NADPH oxidase inhibitor apocynin failed to block ritonavir- or lopinavir-induced currents, although it blocks I_Cl,swell elicited by osmotic swelling or stretch. In contrast, rotenone, a mitochondrial e⁻ transport inhibitor, suppressed both ritonavir- and lopinavir-induced I_Cl,swell. ROS production was measured in HL-1 cardiomyocytes with C-H₂DCFDA-AM and mitochondrial membrane potential (ΔΨ_m) with JC-1. Flow cytometry confirmed that ritonavir and lopinavir but not amprenavir, nelfinavir, or raltegravir augmented ROS production, and HIV PI-induced ROS production was suppressed by rotenone but not NADPH oxidase blockade. Moreover, ritonavir, but not amprenavir, depolarized ΔΨ_m. These data suggest ritonavir and lopinavir activated I_Cl,swell via mitochondrial ROS production that was independent of NADPH oxidase. ROS-dependent modulation of I_Cl,swell and other ion channels by HIV PI may contribute to some of their actions in heart and perhaps other tissues.     

A study of temporal relation between intracellular pH and contractile performance in toad ventricular strips during hypercapnic acidosis

Experiments were performed on toad (Bufo marinus) ventricular strips to determine the temporal relation between the decrease in intracellular pH (pH_i) and the changes in mechanical performance accompanying increases in P_CO2. Changes in pH_i were measured with a dual wavelength spectrophotometer using the pH sensitive dye neutral red. Regardless of whether the superfusate pH (pH₀) or [HCO₃^?] was held constant, changes in P_CO2 were accompanied by a monotonic, biphasic change in pH_i. A plot of 1n ΔpH_i v. t consistently yielded a curvilinear line which was well fit by two straight lines. The developed tension also exhibited a biphasic response to ΔP_CO2: an initial decrease followed by a rebound which returned τ to control values (98.4 ± 1.6%) after 30 min. The onset of the second, slow phase of acidification correlated well (r = 0.83) with the onset of the mechanical rebound. The time of this onset was affected by [HCO₃^?]. Further experiments showed that with P_CO2 held constant, a decrease in [HCO₃^?] was accompanied by a slow decrease in pH_i. The data from these experiments suggest that: (1) changes in P_CO2 affect the pH of at least two intracellular compartments and these effects are temporally dissociated; (2) the response of the faster compartment correlates with the initial decrease of τ; the response of the slower with the rebound of τ; (3) when P_CO2 is held constant, decreases in pH₀ are accompanied by a slow decrease in pH_i suggesting a possible H⁺ or [HCO₃^?] leak.     

Functional role of CLC-2 chloride inward rectifier channels in cardiac sinoatrial nodal pacemaker cells

A novel Cl⁻ inward rectifier channel (Cl,ir) encoded by ClC-2, a member of the ClC voltage-gated Cl⁻ channel gene superfamily, has been recently discovered in cardiac myocytes of several species. However, the physiological role of Cl,ir channels in the heart remains unknown. In this study we tested the hypothesis that Cl,ir channels may play an important role in cardiac pacemaker activity. In isolated guinea-pig sinoatrial node (SAN) cells, Cl,ir current was activated by hyperpolarization and hypotonic cell swelling. RT-PCR and immunohistological analyses confirmed the molecular expression of ClC-2 in guinea-pig SAN cells. Hypotonic stress increased the diastolic depolarization slope and decreased the maximum diastolic potential, action potential amplitude, APD₅₀, APD₉₀, and the cycle-length of the SAN cells. These effects were largely reversed by intracellular dialysis of anti-ClC-2 antibody, which significantly inhibited Cl,ir current but not other pacemaker currents, including the hyperpolarization-activated non-selective cationic “funny” current (I_f), the L-type Ca²⁺ currents (I_Ca,L), the slowly-activating delayed rectifier I_Ks and the volume-regulated outwardly-rectifying Cl⁻ current (I_Cl,vol). Telemetry electrocardiograph studies in conscious ClC-2 knockout (Clcn2^−/−) mice revealed a decreased chronotropic response to acute exercise stress when compared to their age-matched Clcn2^+/+ and Clcn2^+/− littermates. Targeted inactivation of ClC-2 does not alter intrinsic heart rate but prevented the positive chronotropic effect of acute exercise stress through a sympathetic regulation of ClC-2 channels. These results provide compelling evidence that ClC-2-encoded endogenous Cl,ir channels may play an important role in the regulation of cardiac pacemaker activity, which may become more prominent under stressed or pathological conditions.     

Inactivation of calcium-activated chloride channels in smooth muscle by calcium/calmodulin-dependent protein kinase

To determine the mechanisms responsible for the termination of Ca²⁺-activated Cl⁻ currents (I_Cl(Ca)), simultaneous measurements of whole cell currents and intracellular Ca²⁺ concentration ([Ca²⁺]_i) were made in equine tracheal myocytes. In nondialyzed cells, or cells dialyzed with 1 mM ATP, I_Cl(Ca) decayed before the [Ca²⁺]_i decline, whereas the calcium-activated potassium current decayed at the same rate as [Ca²⁺]_i. Substitution of AMP-PNP or ADP for ATP markedly prolonged the decay of I_Cl(Ca), resulting in a rate of current decay similar to that of the fall in [Ca²⁺]_i. In the presence of ATP, dialysis of the calmodulin antagonist W7, the Ca²⁺/calmodulin-dependent kinase II (CaMKII) inhibitor KN93, or a CaMKII-specific peptide inhibitor the rate of I_Cl(Ca) decay was slowed and matched the [Ca²⁺]_i decline, whereas H7, a nonspecific kinase inhibitor with low affinity for CaMKII, was without effect. When a sustained increase in [Ca²⁺]_i was produced in ATP dialyzed cells, the current decayed completely, whereas in cells loaded with 5′-adenylylimidodiphosphate (AMP-PNP), KN93, or the CaMKII inhibitory peptide, I_Cl(Ca) did not decay. Slowly decaying currents were repeatedly evoked in ADP- or AMP-PNP-loaded cells, but dialysis of adenosine 5′-O-(3-thiotriphosphate) or okadaic acid resulted in a smaller initial I_Cl(Ca), and little or no current (despite a normal [Ca²⁺]_i transient) with a second stimulation. These data indicate that CaMKII phosphorylation results in the inactivation of calcium-activated chloride channels, and that transition from the inactivated state to the closed state requires protein dephosphorylation.     

Characteristics of normal rabbit pleural fluid: Physiologic and biochemical implications

Each normal rabbit pleural space contains approximately 0.2 ml of collectable, clear liquid. This fluid has a total cell count of 1503±414 cells/mm³, the majority of which are monocytic cells. Pleural fluid total protein concentration (1.4±0.1 gm/100 ml) is approximately 20%, and lactic dehydrogenase concentration (129±6 Wrobleski U/ml) is approximately 40% of that found in blood. Pleural fluid and blood glucose were equivalent, and venous serum chloride concentration was slightly higher than the simultaneously measured pleural fluid value. Normal rabbit pleural fluid is alkaline; the value of 7.66±0.02 probably is slightly higher than the actual pH value owing to the escape of CO₂. A 8–9 mEq/liter HCO ₃ ⁻ gradient was found between pleural fluid and venous blood. The HCO ₃ ⁻ gradient cannot be explained by the Gibbs-Donnan equilibrium, suggesting that a process of active transport, possibly chloride pumping, is involved.     

Glucose utilization by edematous rat lungs

Edema was produced in the isolated perfused rat lung by raising left atrial pressure. Eleven control lungs consumed 18±3.9 µmoles glucose/lung · hr⁻¹ and released 17.1±4.2 µmoles lactate/lung · hr⁻¹. During pulmonary edema in 13 isolated perfused lungs, glucose consumption was 35.5±8.8 µmoles/lung · hr⁻¹ (P<.05) and lactate production was 37±5.9 µmoles/lung · hr⁻¹ (P<.05). Separation of radiolabeled glucose and lactate indicated that all lactate was derived from glucose in control and edematous lungs. We found no important difference in¹⁴CO₂ production from 1-¹⁴C, 6-¹⁴C, or¹⁴C(U)-glucose. Tissue slices of lungs made edematous in vivo had differences in glucose consumption and lactate production which were similar to those observed in the isolated lungs. Oxygen consumption by 1 mm thick lung slices was 224±9.7 µl O₂/mg DNA · hr⁻¹ in control and 218±18 µl O₂/mg DNA · hr⁻¹ in edematous lungs. When dinitrophenol was added to the medium, the QO₂ was greater in the control than in the edematous lung slices (391±22 µl O₂/mg DNA · hr⁻¹ control vs. 334±33 µl O₂/mg DNA · hr⁻¹ edema,P<.05). We concluded that pulmonary edema in the isolated rat lung is accompanied by: 1) greater glucose consumption; 2) greater lactate production; 3) no important difference in¹⁴CO₂ production from pentose pathway or tricarboxylic cycle activity; and 4) lower response of edematous tissue slices to dinitrophenol stimulation.