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PubMed1975

Relation between length, isometric force, and O2 consumption rate in vascular smooth muscle.

The length-tension and length-oxygen consumption rate relationships were studied in bovine mesenteric vein at 37 degrees C. The absence of spontaneous mechanical activity permits straightforward interpretation in terms of active (smooth muscle) and passive components of the vein wall. Longitudinal loops, the predominant smooth muscle component being oriented in the longitudinal (axial) direction, were maximally stimulated using epinephrine (2-5 mug-ml-1). An optimum length for isometric tension development was exhibited at which the passive tension was 25% of the total tension. The population regression indicated that tension was developed at lengths which ranged from 0.33 to 1.41 times the length at which maximum tension was developed. Oxygen consumption was measured using a Clark-type polarographic electrode. Basal oxygen consumption was 0.432 plus or minus 0.014 (n equal to 121) mumol-min-1 (g dry wt)-1. The basal rate was found to be independent of the passive tension. Under conditions of maximal stimulation, the oxygen consumption rate at L-o, the resting length at which the tissue maintained 1 g-wt passive tension, was approximately twice the basal rate. The length dependence of the suprabasal oxygen consumption was parallel to that of the active isometric force. This parallel relation reflected a linear relation between active isometric force (deltaP-o) and suprabasal oxygen consumption rate (deltaJ-o2). The slope of the deltaJ-o2-deltaP-o linear regression was 0.142 plus or minus 0.013 nmol O2-MIN-1 (G-WT-CM)-1. DeltaJ-o2 at the minimum contracted length, at which no active force was developed, was 15-20% of the deltaJ-o2 measured when maximum isometric force was developed. This provides an upper bound to the rate of chemical energy utilization required for activation processes. The length dependence of active isometric force and chemical energy utilization is most simply interpreted in terms of a sliding-filament model.

Animals↗

PubMed2002

Angiotensin II regulates oxygen consumption.

Previous studies demonstrated that angiotensin II (ANG II) decreases body weight. This study examined whether ANG II regulates body weight through energy expenditure. Acute ANG II administration decreased oxygen consumption. To determine whether this effect was maintained, rats were infused with ANG II or saline for 14 days. Oxygen consumption was transiently decreased on day 1 of ANG II infusion; however, body weight and food intake were reduced for 14 days. In pair-feeding studies, reductions in food intake accounted for 63% of the effect of ANG II on body weight but did not influence systolic pressure, water intake, or oxygen consumption. With 28 days of ANG II infusion, differences in body weight between ANG II and control rats were of greater magnitude. An initial decrease in oxygen consumption was followed by a rebound increase. Coadministration of losartan prevented the effect of ANG II on body weight, food intake, blood pressure, and water intake. However, losartan only partially prevented ANG II reductions in oxygen consumption. These results demonstrate that ANG II transiently decreases oxygen consumption through mechanisms unrelated to food intake. With chronic ANG II exposure, energy expenditure may contribute to sustained reductions in body weight.

Adipose Tissue↗

PubMed1996

Near-infrared estimation of O2 supply and consumption in forearm muscles working at varying intensity.

We estimated a blood flow index, O2 supply index, and O2 consumption index from near-infrared (NIR) signals during venous occlusion imposed at rest and immediately after handgrip exercise with loads equal to 5, 10, 15, 20, 25, and 30% of the maximum voluntary contraction. We also estimated forearm blood flow (BFfa) by strain-gauge plethysmography and forearm O2 consumption (VO2fa) by the invasive method. There was a significant correlation between the rate of increase in total hemoglobin during venous occlusion obtained from NIR signals and BFfa in each subject (r = 0.853 approximately 0.981, P < 0.001). There was also a significant correlation (r = 0.854 approximately 0.944, P < 0.001) between the O2 consumption index estimated from NIR signals and VO2fa. The mean values for O2 supply index in five subjects increased with exercise intensity, while the O2 consumption index showed no further increase about 25% of maximum voluntary contraction. We found significant positive correlations between the O2 supply index and BFfa (r = 0.986, P < 0.001) and the O2 consumption index and VO2fa (r = 0.976, P < 0.001) during exercise at 5-30% of maximum voluntary contraction. These results demonstrate that analysis of NIR signals during venous occlusion provides an advantageous method of estimation of O2 supply and consumption in working muscles during exercise of varying intensity.

Adult↗

PubMed2003

Regional differences in blood flow and oxygen consumption in resting muscle and their relationship during recovery from exhaustive exercise.

This investigation evaluated regional differences in blood flow and oxygen consumption and their relationship in exercised muscle during recovery from exhaustive exercise. Five healthy men performed exhaustive one-legged cycling exercise. Positron emission tomography was used to measure blood flow, oxygen uptake, and oxygen extraction in the quadriceps femoris muscle before and after exercise. Regions of interest included five areas of the muscle (two proximal, one central, and two distal), which were evenly spaced across the muscle. Before exercise, blood flow and oxygen consumption decreased significantly (P < 0.05) in the direction from the proximal to the distal portions; blood flow declined from 2.0 +/- 0.5 to 1.4 +/- 0.3 ml x 100 g-1 x min-1, and oxygen consumption decreased from 0.21 +/- 0.04 to 0.17 +/- 0.02 ml.100 g-1x min-1. In contrast, these gradients in blood flow and oxygen consumption diminished during recovery after exercise. Consequently, there was a positive relationship between changes in blood flow and oxygen consumption in an exercised muscle during recovery after exercise (r = 0.963, P < 0.01). These changes became larger in the direction from proximal to distal portions: blood flow increased from 2.9 +/- 0.7 to 3.9 +/- 0.8 and oxygen consumption from 1.4 +/- 0.1 to 1.8 +/- 0.4 times resting values. These results suggest that hemodynamic variables are heterogeneous within a muscle both at rest and during recovery from exercise and that there is a systematic difference in these variables in the direction from proximal to distal regions within the quadriceps femoris muscle.

Adult↗

PubMed1997

Modulators of nitric oxide in porcine endotoxemia: effects on hepatic oxygen delivery and consumption.

In a porcine model of endotoxemia we have studied the effects of nitric oxide (NO) on hepatic oxygen delivery and consumption. After 3 h of endotoxemia, NO biosynthesis was modulated by a bolus dose of the NO synthase inhibitor NG-nitro-L-arginine methyl ester (L-NAME). Fifteen minutes thereafter a continuous infusion of the NO donor sodium nitroprusside (SNP) was started. Endotoxin significantly reduced hepatic oxygen delivery from 3.4 +/- 0.6 to 2.2 +/- 0.3 ml/kg/min at 3 h. Due to an increased extraction ratio (ER), oxygen consumption was nearly unaffected. L-NAME further diminished oxygen delivery to 1.0 +/- 0.2 ml/kg/min within 15 min (p < 0.05), but despite an increase in ER from 47 to 68% (p < 0.05), oxygen consumption tended to decrease (from 1.0 to 0.7 ml/ kg/min, nonsignificant). A similar tendency was observed in a control group of 9 pigs which was treated in the same way as the study group, except for the SNP infusion. SNP induced an almost selective increase in hepatic arterial flow, with a corresponding increase in oxygen delivery to 1.8 +/- 0.3 ml/kg/min (p < 0.05). At the same time ER was reduced from 68 to 42% (p < 0.05). Oxygen consumption remained unaltered. The control group exhibited no change in either oxygen delivery or consumption. The study shows that nonselective inhibition of NO synthesis is detrimental to hepatic perfusion and oxygen transport. The NO donor SNP increased oxygen delivery via a selective increase in hepatic arterial flow, but failed to influence oxygen consumption. This was probably mainly due to a massive shutdown of sinusoids, which did not reopen when flow was increased. A functioning microcirculation thus seems to be a prerequisite for the stimulation of organ blood flow to be effective.

Animals↗

PubMedDate not supplied

Measuring cardiac output in critically Ill patients: disagreement between thermodilution-, calculated-, expired gas-, and oxygen consumption-based methods.

Calculated values of oxygen consumption have been used to calculate a Fick cardiac output when thermodilution measurements are unreliable and when oxygen consumption measurements are unavailable. To determine the accuracy of these calculations, we measured cardiac output in 20 patients by four methods: (1) a reference Fick cardiac output calculated from metabolic oxygen consumption measurements and arterial-venous oxygen content difference (COmet); (2) thermodilution cardiac output (COtherm), (3) an estimated Fick cardiac output based on calculated oxygen consumption using standard equations (COcalc), and (4) an estimated Fick cardiac output using a bedside measurement of expired carbon dioxide production (COexp). The mean difference +/- 95% limits of agreement between COtherm and COmet was 1.71 +/- 5 liters/min. The mean difference between COcalc and COmet was -0.04 +/- 3.33 liters/min. The mean difference between COexp and COmet was 0.31 +/- 3.01 liters/min. On the basis of these wide confidence intervals, we conclude that (1) thermodilution and metabolic measurements of cardiac output frequently differ in critically ill patients, and (2) estimates of oxygen consumption, based on either standard equations or on expired carbon dioxide production measurements, are poor substitutes for metabolic measurements of oxygen consumption in critically ill subjects and may provide inaccurate estimates of cardiac output.

Adult↗

PubMed1999

Myocardial oxygen consumption is unchanged but efficiency is reduced in patients with essential hypertension and left ventricular hypertrophy.

BACKGROUND: Patients with hypertension and left ventricular hypertrophy (LVH) are prone to develop heart failure. We tested the hypothesis that compensatory LVH is associated with normalization of myocardial oxygen consumption and that this occurs at the expense of a decrease in the ratio between cardiac work and oxygen consumption (efficiency). METHODS AND RESULTS: Nine hypertensive men with LVH (LVH+) (age 42+/-2 years), left ventricular mass index (LVMI) 161+/-8 g/m(2), blood pressure (BP) 145+/-16/88+/-10 mm Hg (mean+/-SD); 8 hypertensive men without LVH (LVH-) (age 39+/-5 years, LVMI 107+/-15 g/m(2), BP 140+/-15/90+/-11 mm Hg); and 10 normotensive men (CONT) were studied. Myocardial blood flow, oxygen consumption, and glucose uptake were measured during euglycemic hyperinsulinemia using PET techniques. LV dimensions, volumes, and workload were determined by echocardiography, and efficiency was calculated. Myocardial workload (2.5+/-0.8 versus 3.0+/-0.6 versus 2. 3+/-0.5 mm Hg. mL. min(-1). g(-1) for CONT versus LVH- versus LVH+; P<0.05, LVH- versus LVH+), myocardial blood flow (0.84+/-0.16 versus 1.06+/-0.22 versus 0.81+/-0.09 mL. g(-1). min, respectively; P<0.05, LVH- versus other groups) and oxygen consumption (0.09+/-0.02 versus 0.14+/-0.03 versus 0.11+/-0.01 ml. g(-1). min(-1), respectively; P<0. 05, LVH- versus other groups) were increased in the LVH- group. Myocardial efficiency was reduced in the LVH+ group (18.1+/-4.1% versus 15.1+/-2.3% versus 13.5+/-1.9%, respectively; P<0.05, LVH+ versus CONT). CONCLUSIONS: Myocardial oxygen consumption per unit weight is increased in hypertensive patients without LVH but is normal in those with LVH. The normalization of oxygen consumption via hypertrophy occurs at the expense of efficiency, which may predispose hypertensive patients with LVH to heart failure.

Adult↗

PubMed1979

Oxygen consumption and hemodynamic response of exercises used in training of patients with recent myocardial infarction.

We investigated oxygen consumption (ml/kg/min) and hemodynamic response (peak heart rate-systolic blood pressure product) to individual exercise activities before and after exercise training in 22 male postmyocardial infarction patients (PMIP). Activities included swimming, walk/jogging, volleyball, calisthenics and exercise dance routines. Oxygen consumption was determined immediately after exercise by the Douglas bag gas collection procedure and, in selected patients, by a Max Planck respirometer during exercise. Hemodynamic data were obtained by pulse count and cuff sphygmomanometer. The increase in oxygen consumption and the decrease in rate-pressure product after each activity were significant (p less than or equal to 0.01). There were no differences in oxygen consumption between the Max Planck respirometer technique and collection (Douglas bag method) immediately after exercise. The oxygen consumption obtained for PMIP compared with available cumulative data on normal subjects is significantly variable, suggesting the need for caution when prescribing exercise for the PMIP based on energy costs of standard exercise measurements in normals. This was particularly relevant because of the significantly high oxygen consumption incurred during swimming.

Body Weight↗

PubMed1989

Noninvasive quantitation of regional myocardial oxygen consumption in vivo with [1-11C]acetate and dynamic positron emission tomography.

The usefulness of [1-11C]acetate as a tracer of overall myocardial oxidative metabolism for use with positron emission tomography has been investigated in 12 closed-chest dogs. Myocardial 11C activity clearance kinetics after intravenous administration of [1-11C]acetate in dogs have been determined noninvasively by positron emission tomography. Biexponential fitting of regional myocardial 11C time-activity curves was performed to give clearance half-times and fractional distribution. The rate constant k1 for the early rapid phase of 11C activity clearance was found to correlate linearly with myocardial oxygen consumption (y = 0.0156x + 0.039; SEE = 0.023; r = 0.95). k1 was approximately 7% lower in septal sectors compared with the left ventricular free wall, suggesting that regional oxygen consumption in the septum was lower; a concomitant regional attenuation of blood flow in the septum relative to the left ventricular free wall was also observed. In dogs using carbohydrates as the predominant fuel, k1 oxygen consumption was somewhat more than in dogs using predominantly free fatty acids (0.021 +/- 0.002 compared with 0.018 +/- 0.002, p less than 0.01), indicating that increased carbohydrate consumption is associated with a small increase in k1 at constant oxygen consumption. It is concluded that measurement of myocardial [1-11C]acetate kinetics allows noninvasive determination of cardiac oxygen consumption by positron emission tomography and that the technique is relatively insensitive to myocardial fuel selection.

Acetates↗

PubMed1978

Quantitative determination of regional oxygen consumption in the dog heart.

A micro-Fick method has been developed to measure the O2 consumption of different regions of an organ. The method was tested in isolated dog gracilis muscle and consisted of microspectrophotometric determination of arterial and venous O2 saturation in quick frozen tissue to determine O2 extraction and flow measured with 85Sr-labeled microspheres, with O2 consumption calculated from the product. This was compared to electromagnetically measured flow and O2 extraction determined by Van Slyke or CO-oximeter. The accuracy of the new measurement was at worst 8.7% for O2 consumption over the range tested in a single muscle. In the hearts of anesthetized open-chest dogs, right ventricular O2 consumption, 7.1 +/- 0.9 ml O2/min per 100 g, was significantly lower than left, 11.0 +/- 0.4. This gradient was related to a blood flow difference. Right ventricular base had a 51% lower O2 consumption than right ventricular apex. In the left ventricle, subepicardial O2 consumption, 9.5 +/- 0.7, was lower than that of the subenocardium, 12.1 +/- 0.7. This difference was related to a difference in O2 extraction.

Animals↗

PubMed1982

Work as a correlate of canine left ventricular oxygen consumption, and the problem of catecholamine oxygen wasting.

Neither stroke volume nor external cardiac work (the integral of pressure times flow during ejection) has been considered an important correlate of myocardial oxygen consumption. An initial set of experiments re-examined this question of independently varying heart rate, systolic blood pressure, and stroke volume in seven closed-chest, anesthetized dogs. This was achieved by cardiac pacing, a pressure control reservoir, phenylephrine infusion, and adjustment of arteriovenous shunts. Propranolol was used to minimize changes in contractility which might affect myocardial oxygen consumption. Stroke volume in the form of external work had a significant effect on oxygen consumption. From these results, a new pressure-work index of myocardial oxygen consumption was devised, and fitting parameters for the following indexes were determined: systolic pressure-rate product, estimated wall tension, external left ventricular work, triple product, mean pressure-rate product, Et (Bretschneider), and tension-time index. These indexes were prospectively applied to a second set of experiments in 11 closed-chest, anesthetized dogs given norepinephrine, isoproterenol, dobutamine, Nembutal, and propranolol to alter myocardial contractility. Inotropic oxygen wasting was observed with the tension-time, mean pressure-rate, triple product, and estimated wall tension indexes, but not with the pressure-work or systolic pressure-rate indexes. It is concluded that stroke work is an important correlate of myocardial oxygen consumption, and that the pressure-work of systolic pressure-rate indexes can account for catecholamine-induced, changes in myocardial oxygen consumption without postulating an oxygen-wasting effect.

Adrenergic beta-Antagonists↗

PubMed1983

Consistent parallel relationships among myocardial oxygen consumption, coronary blood flow, and pericardial infusate adenosine concentration with various interventions and beta-blockade in the dog.

Coronary blood flow responds uniquely to changes in myocardial demand, regardless of the stimulus. If adenosine mediates this response, interstitial fluid adenosine concentration should also change in parallel with myocardial oxygen consumption and coronary blood flow during alterations of cardiac work. We tested this hypothesis by measuring coronary blood flow, myocardial oxygen consumption, and the concentration of adenosine in pericardial infusates, an index of interstitial fluid adenosine concentration, during six experimental conditions and control states in anesthetized, open-chest dogs. Significant alterations of myocardial oxygen consumption and coronary blood flow during aortic constriction, vagal stimulation, atrial pacing, or intravenous infusion of calcium chloride, norepinephrine, or isoproterenol were accompanied by significant alterations in pericardial infusate adenosine concentration. Significant linear relationships were determined among myocardial oxygen consumption, coronary blood flow, and pericardial infusate adenosine concentration for each of the experimental stimuli and their paired control values. There were no significant differences among the six different conditions for any of these relationships. In addition, these relationships were not altered by beta-blockade in five dogs subjected to aortic constriction and calcium infusion. Although beta-blockade may alter the effects of a stimulus, myocardial oxygen consumption, coronary blood flow, and adenosine all are affected proportionately. The results suggest that adenosine production responds to alterations of myocardial oxygen consumption independently of the stimulus which produces the change in oxygen demand, and the resultant change in interstitial fluid adenosine concentration may initiate the change in coronary blood flow to maintain the balance between oxygen supply and demand.

Adenosine↗

PubMed1985

Calcium-dependent enhancement of myocardial diastolic tone and energy utilization dissociates systolic work and oxygen consumption during low sodium perfusion.

The relationships and correlations among functional, metabolic, and ionic consequences of low sodium perfusion were studied in isovolumic, retrograde-aortic perfused working rat hearts by 31P nuclear magnetic resonance, oxygen consumption, and atomic absorption spectrometry. Reduction of perfusate sodium from 144 to 74, 51, 39, and 25 mM in four separate groups of hearts via lithium substitution for 15 minutes decreased cell sodium to mean values of 62, 51, 43, and 36 mumol/g dry weight, respectively (P less than 0.001 vs. control of 107). There was a transient rise and then a fall in developed pressure and a decline in phosphocreatine and adenosine triphosphate, all of which were graded and correlated with perfusate sodium (P less than 0.01 for all parameters vs. perfusate sodium). This was accompanied by a 2- to 7-fold elevation of diastolic pressure while oxygen consumption remained near control levels. All parameters except adenosine triphosphate returned toward baseline values when normal perfusate sodium was reintroduced. Although cell calcium as measured by atomic absorption spectrometry did not differ among the groups, the functional and metabolic changes did not occur if the sodium steps were performed in reduced perfusate calcium (0.08 mM). In hearts in which systolic function was obliterated by verapamil, exposure to zero sodium caused a 4-fold increase in oxygen consumption, an increase in diastolic pressure, and a reduction of high energy phosphates. In the presence of ryanodine, a specific inhibitor of sarcoplasmic reticulum calcium release, the metabolic changes did not occur, and the excess oxygen consumption in zero sodium was substantially reduced. Thus, the effect of lowered perfusate sodium in beating hearts, i.e., to dissociate oxygen consumption and systolic function, and to increase diastolic pressure and its effect in arrested hearts to increase oxygen consumption, are calcium dependent, energy consuming, and modulated by sarcoplasmic reticulum calcium cycling.

Adenosine Triphosphate↗

PubMed1998

Role of nitric oxide in the control of renal oxygen consumption and the regulation of chemical work in the kidney.

Inhibition of NO synthesis has recently been shown to increase oxygen extraction in vivo, and NO has been proposed to play a significant role in the regulation of oxygen consumption by both skeletal and cardiac muscle in vivo and in vitro. It was our aim to determine whether NO also has such a role in the kidney, a tissue with a relatively low basal oxygen extraction. In chronically instrumented conscious dogs, administration of an inhibitor of NO synthase, nitro-L-arginine (NLA, 30 mg/kg i.v.), caused a maintained increase in mean arterial pressure and renal vascular resistance and a decrease in heart rate (all P<0.05). At 60 minutes, urine flow rate and glomerular flow rate decreased by 44+/-12% and 45+/-7%, respectively; moreover, the amount of sodium reabsorbed fell from 16+/-1.7 to 8.5+/-1.1 mmol/min (all P<0.05). At this time, oxygen uptake and extraction increased markedly by 115+/-37% and 102+/-34%, respectively (P<0.05). Oxygen consumption also significantly increased from 4.5+/-0.6 to 7.1+/-0.9 mL O2/min. Most important, the ratio of oxygen consumption to sodium reabsorbed increased dramatically from 0.33+/-0.07 to 0.75+/-0.11 mL O2/mmol Na+ (P<0.05), suggesting a reduction in renal efficiency for transporting sodium. In vitro, both a NO-donating agent and the NO synthase-stimulating agonist bradykinin significantly decreased both cortical and medullary renal oxygen consumption. In conclusion, NO plays a role in maintaining a balance between oxygen consumption and sodium reabsorption, the major ATP-consuming process in the kidney, in conscious dogs, and NO can inhibit mitochondrial oxygen consumption in canine renal slices in vitro.

Animals↗

PubMed1992

Changes in oxygen consumption in dog gingiva during induction of experimental periodontitis.

The purpose of this study was to examine changes in oxygen consumption in dog gingiva during induction of experimental periodontitis. The disease was induced in adult mongrel dogs during a 16-week period by placement of silk ligatures around selected teeth. The oxygen consumption rate of gingival tissue was determined in vivo by a non-invasive technique, tissue reflectance spectrophotometry. Changes in such clinical parameters as gingival index, plaque index, pocket depth, attachment level, and gingival crevicular fluid flow indicated acute inflammatory responses during the first three weeks after ligation, followed by the appearance of chronic inflammation during the remaining 13 weeks. The oxygen consumption rate increased during the first seven days after ligation and stayed near the maximum level for 2-7 weeks; this was followed by a gradual decrease during the final nine weeks. These results suggest that gingival oxygen consumption increases rapidly with the increase of acute inflammation responses and then decreases slightly with the gradual development of chronic inflammation. Positive correlations were observed between the oxygen consumption rate and other clinical indices. Thus, the tissue reflectance spectrophotometry is a new, useful method for objective, quantitative, and non-invasive assessment of gingival oxygen consumption.

Animals↗

PubMed2003

Determination of oxygen consumption for landfilled municipal solid wastes.

One of the serious problems of landfilling is the long time required for stabilisation. Nevertheless, site aeration proved to be effective to attenuate such problems. Oxygen consumption rate and air permeability/diffusion are the key parameters to set up the best allocation and design for vertical pipes to promote aeration and hence stabilisation of waste. This paper presents an investigation into the oxygen consumption for various landfilled wastes in Japan such as incineration ash, incombustible waste and under-sieve fraction of shredded bulky waste. Fresh waste sampled directly from processing facilities, as well as old waste sampled from landfill sites, were subjected to analytical determination and measurement of oxygen consumption. Bulky waste showed the highest oxygen consumption, however the old waste revealed a significant loss of biodegradability potential and lower oxygen consumption records. The oxygen consumption for short testing periods (10-days), tends to increase with the ignition loss (IL). The experimental data of respiratory tests (for old waste) were modelled and the fitting parameters are correlated to waste characteristics.

Biodegradation, Environmental↗

PubMed1981

Myocardial consumption of oxygen and carbohydrates in newborn sheep.

We measured blood flow to the myocardium of the left ventricular free wall, and blood glucose, lactate, pyruvate, and oxygen concentrations simultaneously in the aorta and coronary sinus 13 times in seven previously instrumented newborn sheep, 4 to 25 days after birth. We calculated arteriovenous difference and consumption of oxygen, glucose, lactate, and pyruvate by the newborn myocardium. Results were compared with recently obtained measurements in the myocardium of fetal and adult sheep (6). Myocardial consumption of oxygen in the newborn (577 +/- 38 microM.min-1.100 g LV-1) was higher than in either the fetuses or the adults. This was associated with a greater myocardial blood flow (201 +/- 21 mm.min-1.100 g LV-1) in the newborns. However, the increased myocardial oxygen consumption in the newborns was commensurate with their increased cardiac work as compared with both the fetuses and adults. Although there is an abrupt postnatal increase in arterial glucose concentration, there was no significant difference in either the myocardial consumption of glucose or the contribution of glucose to the total myocardial energy supply among fetal, newborn or adult sheep. Postnatal decreases in myocardial consumption of lactate and pyruvate are not compensated for by an increase in glucose consumption. In newborn sheep, carbohydrates including glucose, lactate, and pyruvate supply the substrate for no more than approximately one-fourth of the total myocardial energy demands (carbohydrate/oxygen quotient was 0.26).

Animals↗

PubMed1982

Oxygen consumption in treadmill-exercised Yucatan miniature swine.

Oxygen consumption was measured in Yucatan miniature swine during various intensities of treadmill exercise. Nine animals were evaluated at rest and at various treadmill velocities ranging from 2.5-4.5 mph. Oxygen consumption was linearly related to treadmill speed during sub-maximal exercise work loads (r = 0.92, P less than 0.01). Maximal oxygen consumption was also determined in two groups of animals. In one group (N = 6) the highest attainable oxygen consumption was 24.0 +/- 1.31 ml . min-1 . kg-1. In the second group (N = 9) an electric prod was utilized to encourage the animals to run. Their maximal oxygen consumptions ranged from 33.9-51.1 ml . min-1 . kg-1 with a mean of 41.7 +/- 1.8 ml . min-1 . kg-1. These data indicated that Yucatan swine have a relatively low aerobic capacity compared to the rat or dog, but their oxygen consumptions are similar to that observed in untrained man.

Animals↗