Red Blood Cell Lactate Research Articles

RED BLOOD CELL DESIALYLATION, AS OBSERVED IN SEPSIS ALTERS THEIR SHAPE AND BIOCHEMISTRY

Introduction: Red blood cell (RBC) metabolism is totally dependent on glycolysis to supply the ATP required for the maintenance of ionic homeostasis and structural integrity (1). Several studies have observed interactions between glycolytic enzymes and the RBC membrane (2,3). We have recently observed that RBCs from septic patients show a more spherical shape with decreased membrane sialic acid (SA) content (4). Moreover, RBC sphericity was inversely correlated with membrane SA content (4). We therefore hypothesized that desialylation as observed in septic patients could alter RBC glycolysis. Materials and Methods: Washed RBCs from 9 volunteers (adjusted at 20% hematocrit) were incubated with 0.125 U/mL of neuraminidase from Clostridium perfringens or RPMI as controls. RBC shape was estimated by flow cytometry after 10 hours of incubation. Normal RBCs show a bimodal distribution related to the biconcave form (4). On this histogram, we calculated the second Pearson Coefficient of Dissymmetry (= 3 × (mean-median)/SD) (PCD). The normal PCD value is around - 0.8 and a null value represents a perfect spherical shape. To confirm the release of SA from the RBC membrane by neuraminidase, free SA concentrations in the supernatant were measured at baseline and after 10 hours of incubation by an enzymatic colorimetric assay. 2,3 DPG and RBC lactate concentrations were measured after 10 hours of incubation with neuraminidase. Data are presented as mean±SD and were compared by a Student's test; correlations were evaluated by a Spearman's test. Results: Neuraminidase altered RBC shape and glycolysis. PCD values were correlated with 2,3 DPG concentrations (r2 = 0.37; P = 0.008).TableConclusions: Desialylation induces RBC sphericity and an increase in RBC lactate and 2,3 DPG concentrations, already present 10 hours after neuraminidase treatment. These changes may play a role in the alterations in RBC rheology observed in sepsis, and could be the target of new interventions to improve the management of septic patients. Funds: Erasme Foundation

Lactate Distribution in the Blood Compartments of Sickle Cell Trait Carriers during Incremental Exercise and Recovery

Whether or not whole blood lactate concentration is the same during a ramp exercise test in subjects with sickle cell trait (AS) as in normal subjects remains a point of controversy in the literature. Some studies have shown that the ability to produce or clear circulating lactate might differ between AS and subjects with normal haemoglobin (AA). If this is indeed so, the lactate distribution in the blood compartments should also differ. To test this hypothesis, lactate concentrations in the whole blood, plasma and red blood cells of AS and AA were compared at rest and in response to exercise. Eight AS and 8 AA performed an incremental exercise test. Whole blood, plasma and red blood cell lactate concentrations, the red blood cell : plasma lactate concentration ratio, the plasma-to-red blood cell lactate gradient, haematocrit and cardiorespiratory variables were analysed at rest and during an incremental exercise test and active recovery. Maximal oxygen uptake and ventilatory thresholds were similar in the two groups. No significant difference in whole blood, plasma or red blood cell lactate concentrations was observed between the two groups at rest, during exercise, or during the immediate recovery. Neither the red blood cell : plasma lactate concentration ratio nor the plasma-to-red blood cell lactate gradient differed between groups. Lactate distribution in the blood compartments did not differ between the two groups and this finding suggests that lactate production and/or clearance is quite similar during exercise in AS and AA.

Faster lactate transport across red blood cell membrane in sickle cell trait carriers

The physical and physiological behavior of sickle cell trait carriers (AS) is somewhat equivocal under strenuous conditions, although this genetic abnormality is generally considered to be a benign disorder. The occurrence of incidents and severe injuries in AS during exercise might be explained, in part, by the lactic acidosis due to a greater lactate influx into AS red blood cells (RBCs). In the present study, the RBC lactate transport activity via the different pathways was compared between AS and individuals with normal hemoglobin (AA). Sixteen Caribbean students, nine AS and seven AA, performed a progressive and maximal exercise test to determine maximal oxygen consumption. Blood samples were obtained at rest to assess haematological parameters and RBC lactate transport activity. Lactate influxes [total lactate influx and monocarboxylate transporter (MCT-1)-mediated lactate influx] into erythrocytes were measured at four external [14C]-labeled lactate concentrations (1.6, 8.1, 41, and 81.1 mM). The two groups had similar maximal oxygen consumption. Total lactate influx and lactate influx via the MCT-1 pathway were significantly higher in AS compared with AA at 1.6, 41, and 81.1 mM. The maximal lactate transport capacity for MCT-1 was higher in AS than in AA. Although AS and AA had the same maximal aerobic physical fitness, the RBCs from the sickle cell trait carriers took up more lactate at low and high concentrations than the RBCs from AA individuals. The higher MCT-1 maximal lactate transport capacity found in AS suggests greater content or greater activity of MCT-1 in AS RBC membranes.

Lactate transport in red blood cells by monocarboxylate transporters.

The lactate transport activity of red blood cells (RBC) varies widely among different species; in equine RBC, the activity of the main lactate carrier, H+-monocarboxylate co-transporter (MCT), is distributed bimodally. The influence of lactate transport activity is measurable in vivo; after maximal exercise, the RBC lactate concentration in horses with high (HT) lactate transport activity is higher than in those with low (LT) activity. To study the expression of MCT in HT and LT horses, blood samples were taken from 10 horses at rest and after submaximal exercise. Blood and plasma lactate concentrations, lactate and pyruvate transport activities and the amounts of MCT1, MCT2 and MCT4 were measured. After exercise, RBC lactate concentration was higher in HT (n = 5) than in LT (n = 5) horses. At lactate concentrations of 0.25-30 mmol/l and at a pyruvate concentration of 1 mmol/l, transport activity was higher in HT horses. At a lactate concentration of 0.1 mmol/l, transport was similar. In Western blots, the signals for MCT1 and MCT2 were similar in both groups. The amount of CD147, a chaperone necessary for the activity of MCT1, was lower in LT horses. We suggest that MCT2 transports lactate at low concentrations, while MCT1 is needed at higher concentrations. MCT1 may be less active in LT horses and, therefore, during exercise their capacity to take up lactate is low. Further studies are needed to show whether the differences in lactate influx in RBC affect the function of erythrocytes or the performance capacity of horses.

Lactate concentration in plasma and red blood cells during incremental exercise.

The purpose of this study was to investigate the distribution of lactate in plasma and red blood cells (RBC) in capillary blood during and after incremental exercise. We measured capillary plasma lactate and whole blood lactate of 10 subjects during incremental treadmill running and the first 20 min of recovery. To minimize lactate exchange from plasma to RBC between sampling and analysis, a recently developed rapid plasma separation method was used. RBC lactate was calculated. The RBC/plasma lactate concentration ratio decreased from 1.0 (0.85-1.28) before to 0.37 (0.25-0.45) after exhaustive exercise (plasma lactate 15.9 (12.2-19.5)mmol x I(-1), RBC lactate 4.8 (4.0-7.0) mmol x 1(-1)), thus showing that capillary plasma lactate increased much more rapidly than intracellular lactate during incremental exercise. In the first 5 minutes of recovery intracellular lactate still rose while plasma lactate already declined. Then both decreased while the concentration ratio as well as the absolute concentration gradient remained nearly constant (ratio 20 min after exercise termination: 0.43 (0.19-0.54).

Factors affecting accumulation of lactate in red blood cells.

In horses, both the post exercise distribution of lactate between plasma and red blood cells (RBC) and the activity of lactate transporters on the RBC membrane vary widely between individuals. In this study, we investigated the effects of pH, time and temperature on lactate distribution in vitro, and compared the in vitro activity of lactate transporters with the accumulation of lactate into RBC in vivo. To accomplish this, we took venous blood samples at rest and after trotting races. The post exercise accumulation of lactate into RBC was shown to depend on the activity of lactate transporters. The results, in vitro, also indicate that pH, incubation time and temperature influence the activity of lactate transporters and the accumulation of lactate into RBC, underscoring the fact that in practice it is important to standardise the measurement conditions of lactate. These results support the view that whole blood lactate concentrations should be measured in estimating the accumulation of lactate from exercising muscles into the blood, because the effect of blood pH, temperature, time to centrifugation of the sample and also interindividual variation in lactate transport into RBC are therefore minimised.

Lactate influx into red blood cells from trained and untrained human subjects.

The purpose of this study was to compare the fractional contributions of the three pathways of lactate transport (band 3 system, nonionic diffusion, and monocarboxylate pathway) into red blood cells (RBC) from trained and untrained humans. Blood samples were obtained from 19 male subjects: 5 untrained, 5 aerobically-trained, 5 competitive collegiate cross-country runners, and 4 competitive collegiate sprinters. The influx of lactate into the RBC was measured by a radioactive tracer technique using [14C]lactate. Discrimination of each pathway of lactate transport was achieved by using PCMBS (1 mM) to block the monocarboxylate pathway and DIDS (0.2 mM) to block the band 3 system. Nonionic diffusion was calculated as the difference between total lactate influx and the sum of band 3 and monocarboxylate lactate influx. Total lactate influx into the RBC from the more aerobic individuals (trained subjects and cross-country runners) was significantly faster at 1.6 mM lactate concentration ([La]) as compared with the influx into RBC of the untrained subjects. Total influx of lactate was significantly higher (P < 0.05) in the RBC from the sprinters as compared with that in the RBC from the untrained subjects at 41 mM [La]. There were no significant differences among the four groups with regard to the total influx of lactate at 4.1, 8.1, and 20 mM [La]. In general, the percentage of total lactate influx accounted for by each of the three parallel pathways at 1.6, 8.1, and 41.0 mM [La] was not different among the four groups of subjects. Overall, the groups were more similar than different with regard to RBC lactate influx.

Distribution of lactate between red blood cells and plasma after exercise

SummaryThe distribution of lactate between blood cells and plasma, lactate concentration in whole blood and plasma, concentration of haemoglobin and packed cell volume (PCV) were measured in Standardbred and Finnhorse trotters. Red blood cell (RBC) lactate was calculated from whole blood and plasma lactate concentrations and PCV. Plasma lactate concentration correlated positively with whole blood lactate concentration over a range of exercise intensities (r = 0.972; P &lt; 0.001). Similarly, plasma lactate concentration correlated with the calculated RBC lactate concentration both after the standardised submaximal exercise test (SET) and races, although there was individual variation in gradients. The slope of regression after the SET increased with sampling time, but such an effect was not found after the races. The mean corpuscular haemoglobin concentration did not show any correlation with RBC lactate concentration. Based on these results, we suggest that transport of lactate to erythrocytes occurs rapidly and is mainly determined by plasma lactate concentration. The great variation between individuals and individual similarity of plasma‐cell concentration differences after submaximal and maximal exercise indicates that distribution of lactate between plasma and erythrocytes depends not only on plasma lactate concentration. Other factors, such as lactate transporter, may be important.

Distribution of lactate in plasma anderythrocytes during and after exercise in horses

The distribution of lactate between red blood cells (RBC) and plasma was examined at rest, during exercise and 30 min after exercise in six Standardbred horses. Lactate and water concentrations were measured in blood and plasma samples collected prior to exercise, during the last 15 s of each step of an incremental exercise test and at 5 min intervals during the first 30 min after exercise. The mean ratio of RBC lactate concentration (RBCLa) to plasma lactate concentration (PLa) prior to exercise was 1.02 +/- 0.34. Haemoconcentration during exercise was associated with more rapid accumulation of lactate in plasma than in RBCs. Mean whole blood lactate concentration (BLa) was only 59% of PLa in samples collected during exercise. BLa was highly correlated with PLa during exercise (r = 0.98; P < 0.001), but individual PLa values differed from predicted BLa values by up to 2.1 mmol l-1 when PLa exceeded 8 mmol l-1. At each exercise speed and time after exercise there was a large variation between horses in the ratio of BLa/PLa. During exercise at 11 m s-1 the ratio ranged from 0.46-0.73. The BLa/PLa ratio was significantly correlated with increasing exercise intensity, (r = -0.68, P < 0.001) and with haematocrit, (r = -0.69, P < 0.001). The effects of PLa and haematocrit on the BLa/PLa ratio during exercise and the post-exercise period varied greatly between horses. The ratio of lactate concentrations in water of RBCs and plasma varied greatly during and after exercise (0.61-1.22). The ratio also varied considerably between horses, with coefficients of variation ranging from 14-34%. Lactate concentrations in RBC and plasma water vary greatly between horses during and after exercise. We concluded that lactate is unevenly distributed between red blood cells and plasma in blood samples centrifuged immediately after collection, and the variability depends on haematocrit.