Dataset Information

[14C]bicarbonate fixation into glucose and other metabolites in the liver of the starved rat under halothane anaesthesia. Metabolic channelling of mitochondrial oxaloacetate.

ABSTRACT: Previous attempts to account for the labelling in vivo of liver metabolites associated with the citrate cycle and gluconeogenesis have foundered because proper allowance was not made for the heterogeneity of the liver. In the basal state (anaesthetized after 24h starvation) this heterogeneity is minimal, and we show that labelling by [14C]bicarbonate can be interpreted unambiguously. [14C]Bicarbonate was infused to an isotopic steady state, and measurements were made of specific radioactivities of blood bicarbonate, alanine, glycerol and lactate, of liver alanine and lactate, and of individual carbon atoms in blood glucose and liver aspartate, citrate and malate. (Existing methods for several of these measurements were extensively modified.) The results were combined with published rates of gluconeogenesis, uptake of gluconeogenic precursors by the liver, and citrate-cycle flux, all measured under similar conditions, and with estimates of other rates made from published data. To interpret the results, three ancillary measurements were made: the rate of CO2 exchange by phosphoenolpyruvate carboxykinase (PEPCK; EC 4.1.1.32) under conditions that simulated those in vivo; the 14C isotope effect in the pyruvate carboxylase (EC 6.4.1.1) reaction (14C/12C = 0.992 +/- 0.008; S.E.M., n = 8); the ratio of labelling by [2-14C]- to that by [1-14C]-pyruvate of liver glutamate 1.5 min after injection. This ratio, 3.38, is a measure of the disequilibrium in the mitochondria between malate and oxaloacetate. The data were analysed with due regard to experimental variance, uncertainties in values of fluxes measured in vitro, hepatic heterogeneity and renal glucose output. The following conclusions were reached. The results could not be explained if CO2 fixation was confined to pyruvate carboxylase and there was only one, well-mixed, pool of oxaloacetate in the mitochondria. Addition of the other carboxylation reactions, those of PEPCK, isocitrate dehydrogenase (EC 1.1.1.42) and malic enzyme (EC 1.1.1.40), was not enough. Incomplete mixing of mitochondrial oxaloacetate had to be assumed, i.e. that there was metabolic channelling of oxaloacetate formed from pyruvate towards gluconeogenesis. There was some evidence that malate exchange across the mitochondrial membrane might also be channelled, with incomplete mixing with that in the citrate cycle. Calculated rates of exchange of CO2 by PEPCK were in agreement with those measured in vitro, with little or no activation by Fe2+ ions.(ABSTRACT TRUNCATED AT 400 WORDS)

SUBMITTER: Heath DF

PROVIDER: S-EPMC1144914 | biostudies-other | 1985 May

REPOSITORIES: biostudies-other

ACCESS DATA

Similar Datasets

Project description:ObjectivesTo determine whether administration of local anaesthetic at the site of skin incision during open lacrimal drainage surgery under general anaesthesia alters the total dosage of anaesthetic drugs required during total intravenous anaesthesia (TIVA), and whether it alters postoperative pain and recovery.Study designMasked comparison of a randomized, two-group interventional study.Patients and methodsPatients undergoing unilateral external dacryocystorhinostomy under total intravenous general anaesthesia were recruited from the lacrimal service at Moorfields Eye Hospital between September 2012 and February 2014. The patients were randomised to receive, after induction and stabilisation of general anaesthesia, infiltration of the ipsilateral paranasal tissues with 2.5 ml of 0.5% bupivacaine with 1:100000 epinephrine ("treatment" group), or a sham injection ("control" group); the infiltration was performed about 7 min prior to the skin incision. The infusion rates for propofol and remifentanil were adjusted to maintain a steady intra-operative mean blood pressure of 55-70 mmHg and BIS score of 40-60%. The time taken for extubation of the patient after cessation of TIVA was recorded, and postoperative pain scores (on a Likert scale from 0-10) were taken at regular intervals after extubation. The average intra-operative mean blood pressures, total drug usage, extubation time and pain scores for each of the two groups were compared using two-tail Student's t-testing and Wilcoxon rank sum testing.ResultsThere were 12 patients (7 female; 58%) in the treatment group and 11 (7 female; 64%) in the control group, with similar average age at surgery (59 years treatment, 53 years control; p = 0.38) The average operative time was 45 min in the treatment group (median 42, range 30-55) and 47 min (median 45; range 37-61) in the control group (p = 0.52). The mean dosage of propofol required to maintain satisfactory GA was significantly less in the "treatment" group (89.8 mcg/kg/min) as compared to the "control" group (mean 126 mcg/kg/min) (p = 0.0007). Likewise, remifentanil dosage was significantly less in the "treatment" group (100 ng/kg/min) as compared to controls (259 ng/kg/min) (p = 0.00007). The mean non-invasive blood pressure was consistently lower during surgery in the "treated" group, and showed less intra-operative variation. After surgery, the patients receiving LA had a significantly shorter extubation time (mean time 6.0 min in "treated" group, 12.1 min in "controls"; P < 0.0002) and also significantly lower pain scores at 10, 30, 60, 120 and 180 min after extubation (p < 0.01, p < 0.01, p < 0.01, p < 0.01 and p < 0.05, respectively).ConclusionsIpsilateral infiltration of local anaesthesia containing epinephrine in the paranasal tissues just prior to open dacryocystorhinostomy under total intravenous anaesthesia is associated with a 28% reduction in mean propofol usage, and a 61% reduction in remifentanil usage. LA usage during GA also produces improved and less variable intra-operative mean blood pressures, a significantly shorter extubation time and significantly lower postoperative pain scores.

Project description:BackgroundRenal dysfunction following intraoperative arterial hypotension is mainly caused by an insufficient renal blood flow. It is associated with higher mortality and morbidity rates. We hypothesised that the intraoperative haemodynamics are more stable during xenon anaesthesia than during isoflurane anaesthesia in patients undergoing partial nephrectomy.MethodsWe performed a secondary analysis of the haemodynamic variables collected during the randomised, single-blinded, single-centre PaNeX study, which analysed the postoperative renal function in 46 patients who underwent partial nephrectomy. The patients received either xenon or isoflurane anaesthesia with 1:1 allocation ratio. We analysed the duration of the intraoperative systolic blood pressure decrease by > 40% from baseline values and the cumulative duration of a mean arterial blood pressure (MAP) of < 65 mmHg as primary outcomes. The secondary outcomes were related to other blood pressure thresholds, the amount of administered norepinephrine, and the analysis of confounding factors on the haemodynamic stability.ResultsThe periods of an MAP of < 65 mmHg were significantly shorter in the xenon group than in the isoflurane group. The medians [interquartile range] were 0 [0-10.0] and 25.0 [10.0-47.5] minutes, for the xenon and isoflurane group, respectively (P = 0.002). However, the cumulative duration of a systolic blood pressure decrease by > 40% did not significantly differ between the groups (P = 0.51). The periods with a systolic blood pressure decrease by 20% from baseline, MAP decrease to values < 60 mmHg, and the need for norepinephrine, as well as the cumulative dose of norepinephrine were significantly shorter and lower, respectively, in the xenon group. The confounding factors, such as demographic data, surgical technique, or anaesthesia data, were similar in the two groups.ConclusionThe patients undergoing xenon anaesthesia showed a better haemodynamic stability, which might be attributed to the xenon properties. The indirect effect of xenon anaesthesia might be of importance for the preservation of renal function during renal surgery and needs further elaboration.Trial registrationClinicalTrials.gov : NCT01839084. Registered 24 April 2013.

Project description:1. [2-(3)H,U-(14)C]- or [3-(3)H,U-(14)C]-Lactate was administered by infusion or bolus injection to overnight-starved rats. Tracer lactate was injected or infused through indwelling cannulas into the aorta and blood was sampled from the vena cava (A-VC mode), or it was administered into the vena cava and sampled from the aorta (V-A mode). Sampling was continued after infusion was terminated to obtain the wash-out curves for the tracer. The activities of lactate, glucose, amino acids and water were followed. 2. The kinetics of labelled lactate in the two modes differed markedly, but the kinetics of labelled glucose were much the same irrespective of mode. 3. The kinetics of (3)H-labelled lactate differed markedly from those for [U-(14)C]lactate. Isotopic steady state was attained in less than 1h of infusion of [(3)H]lactate but required over 6h for [U-(14)C]lactate. 4. (3)H from [2-(3)H]lactate labels glucose more extensive than does that from [3-(3)H]lactate. [3-(3)H]Lactate also labels plasma amino acids. The distribution of (3)H in glucose was determined. 5. Maximal radioactivity in (3)HOH in plasma is attained in less than 1min after injection. Near-maximal radioactivity in [(14)C]glucose and [(3)H]glucose is attained within 2-3min after injection. 6. The apparent replacement rates for lactate were calculated from the areas under the specific-radioactivity curves or plateau specific radioactivities after primed infusion. Results calculated from bolus injection and infusion agreed closely. The apparent replacement rate for [(3)H]lactate from the A-VC mode averaged about 16mg/min per kg body wt. and that in the V-A mode about 8.5mg/min per kg body wt. The apparent rates for [(14)C]lactate (;rate of irreversible disposal') were 8mg/min per kg body wt. for the A-VC mode and 5.5mg/min per kg body wt. for the V-A mode. Apparent recycling of lactate carbon was 55-60% according to the A-VC mode and 35% according to the V-A mode. 7. The specific radioactivities of [U-(14)C]glucose at isotopic steady state were 55% and 45% that of [U-(14)C]lactate in the A-VC and V-A modes respectively. We calculated, correcting for the dilution of (14)C in gluconeogenesis via oxaloacetate, that over 70% of newly synthesized glucose was derived from circulating lactate. 8. Recycling of (3)H between lactate and glucose was evaluated. It has no significant effect on the calculation of the replacement rate, but affects considerably the areas under the wash-out curves for both [2-(3)H]- and [3-(3)H]-lactate, and calculation of mean transit time and total lactate mass in the body. Corrected for recycling, in the A-VC mode the mean transit time is about 3min, the lactate mass about 50mg/kg body wt. and the lactate space about 65% of body space. The V-A mode yields a mass and lactate space about half those with the A-VC mode. 9. The area under the wash-out curve for [(14)C]lactate is some 20-30 times that for [(3)H]lactate, and apparent carbon mass is 400-500mg/kg body wt. and presumably includes the carbon of glucose, pyruvate and amino acids, which are exchanging rapidly with that of lactate.

Dataset Information

[14C]bicarbonate fixation into glucose and other metabolites in the liver of the starved rat under halothane anaesthesia. Metabolic channelling of mitochondrial oxaloacetate.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets