Increased Mean Corpuscular Hemoglobin Concentration Research Articles

Increased MCHC*RDW-SD interaction values: indicators of neurological impairment in lead-poisoned children.

The neurotoxic effects of lead in children can have long-lasting and profound impacts on the developing nervous system. This study aimed to identify a reliable and easily accessible biomarker to monitor neurological impairment in lead-poisoned children. We analyzed hematological data from 356 lead-poisoned children, comparing them with age and gender-matched healthy controls. Multivariate logistic regression and receiver operating characteristic (ROC) analysis were employed to identify and evaluate potential biomarkers for neurological damage. Significant changes in erythrocyte parameters were observed in lead-poisoned children. Upon further analysis, increased mean corpuscular hemoglobin concentration (MCHC) and red cell distribution width-standard deviation (RDW-SD) interaction values were found to be significantly associated with neurological impairment. The MCHC*RDW-SD interaction model demonstrated an AUC of 0.76, indicating its effectiveness in reflecting neurological damage. Additionally, the MCHC*RDW-SD Interaction value showed weak or no correlation with other erythrocyte parameters, suggesting its independence as an indicator. Our findings propose the increased MCHC*RDW-SD interaction value as a robust and independent biomarker for detecting neurological impairment in lead-poisoned children. This underscores the potential of utilizing specific erythrocyte parameters for screening the neurotoxic effects of lead exposure in pediatric populations.

Evaluation of a novel heparin-iloprost-based antithrombotic formulation blood collection tube for clinical usage

BackgroundThe objective of our study was to evaluate a single blood collection tube with a novel antithrombotic formulation to measure both hematological, biochemical, and d-dimer analytes. MethodsPaired samples of gold standard blood tubes (EDTA, lithium heparin, sodium citrate) and a new antithrombotic formulation blood tube were collected from 187 patients. The new antithrombotic tube is a lithium heparin tube preloaded with a liquid form of prostacyclin analog. The novel tube was tested on seventeen hematological parameters and smears against EDTA, on fourteen biochemical parameters against lithium heparin and on d-dimer against sodium citrate. ResultsAll correlation coefficients were close to 0.99. The Bland-Altman analyses presented a satisfactory correspondence for all analytes. All the hematological examinations demonstrated comparable results between EDTA and the novel formulation, except for platelet counts analyzed by impedance method, but not by fluorescence. We detected lower mean platelet volume with/without outliers (5.06%)/(5.13%) in the novel formulation and increased mean corpuscular hemoglobin concentration (2.55%). All the biochemistry analytes demonstrated comparable results between lithium heparin and the novel tube. d-dimer showed comparable results between citrated blood and the novel formulation after dilution correction. ConclusionsWe describe a novel antithrombotic formulation tube with the potential to be introduced into clinical laboratories for simultaneous analysis of thirty-two blood analytes.

A novel PIEZO1 mutation in a patient with dehydrated hereditary stomatocytosis: a case report and a brief review of literature

BackgroundDehydrated hereditary stomatocytosis (DHS) or hereditary xerocytosis is a rare, autosomal dominant hemolytic anemia characterized by macrocytosis, presence of stomatocytes and dehydration of red blood cells (RBCs). The dehydration is caused by a defect in cellular cation content. The most frequent expression of the pathology is hemolytic well-compensated anemia with high reticulocyte count, a tendency to macrocytosis, increased mean corpuscular hemoglobin concentration (MCHC) and mild jaundice. We here describe a new mutation of PIEZO1 gene, the most frequent mutated gene in DHS, in a family affected by hereditary hemolytic anemia.Case presentationWe describe the case of a 12-years-old girl with well-compensated chronic hemolysis, increased MCHC and a father who had the same hematological characteristics. After excluding secondary causes of chronic hemolysis and enzymatic defects of the RBCs, microscopic observation of the peripheral blood smear, tests of RBC lysis, ektacytometry, SDS-PAGE and in last instance genetic analysis has been performed. This complex diagnostic workup identified a new variant in the PIEZO1 gene, never described in literature, causative of DHS. This pathogenetic variant was also detected in the father.ConclusionsThis case report highlights the importance of a correct and exhaustive diagnostic-workup in patients with clinical suspicious for hemolytic anemia in order to make a differential diagnosis. This is relevant for the management of these patients because splenectomy is contraindicated in DHS due to high thrombotic risk.

Heterogeneous phenotype of Hereditary Xerocytosis in association with PIEZO1 variants

Hereditary Xerocytosis (HX) is an autosomal dominantly inherited congenital hemolytic anemia associated with erythrocyte dehydration due to decreased intracellular potassium content resulting in increased mean corpuscular hemoglobin concentration. The affected members of HX families show compensated anemia with splenomegaly, hemosiderosis, and perinatal edema but are in large part transfusion independent. Functional studies show a link between mutations in mechanosensitive ion channel, encoded by PIEZO1 gene and the HX. We identified new PIEZO1 variants that are likely pathogenic in three phenotypically characterized multi-generational HX Brazilian families. Interestingly, one missense variant of the PIEZO1 gene identified, p.E2494V was associated in trans with the previously reported most frequent pathogenic duplication p.E2496ELE. The three-dimensional structure of the human protein modeled using structural coordinates of the mouse Piezo1 solved by cryo-electron microscopy (Cryo-ME) showed that the two identified variants, p.M2007L and p.T2014I, are localized to an important mechanosensitive transmembrane domain suggesting a conformational mechanism for altered channel's gating. The p.E2496ELE variant identified alters the extension of helix α1 bringing it much closer to the beam affecting the position of it structure at the end of the pore.

Dietary supplementation with L-lysine affects body weight and blood hematological and biochemical parameters in rats.

L-Lysine (Lys) is a popular additive in foods, but the physiological effects of excess Lys supplementation are poorly understood and upper limits of safe intake have not been established. The objectives of this study were to examine the effects of dietary supplementation with increasing amounts of Lys on body weight (BW), food intake, and various blood hematological and biochemical parameters in rats. Male Sprague-Dawley rats at 10weeks of age were assigned to ten diet groups (eight rats/group) and fed diets containing either 7% or 20% casein and supplemented with either 0% (Control), 1.5%, 3%, 6% Lys, or 6% Lys + 3% arginine for 1 week. Rats fed 7% casein with ≥ 1.5% Lys supplementation had lower serum albumin and leptin and higher LDL cholesterol (LDLC), ratios of total cholesterol (TC):HDL cholesterol (HDLC) and LDLC:HDLC than those fed 7% casein Control diet (P < 0.05). Rats fed 7% casein diet supplemented with 3% Lys diet had lower BW gain, food intake, serum alkaline phosphatase activity, and increased mean corpuscular hemoglobin concentration, blood urea nitrogen and serum pancreatic polypeptide compared to rats fed the Control diet (P < 0.05). Addition of 6% Lys in 7% casein caused significant BW loss (P < 0.001) and altered additional parameters. Addition of 6% Lys in a 20% casein diet reduced BW gain and food intake and altered numerous parameters. Arg supplementation normalized many of the endpoints changed by Lys. Collectively, these results show that Lys supplementation affects BW, food intake and a number of hematological and biochemical parameters. These effects of Lys supplementation were confined primarily in diets with lower levels of dietary protein. In the context of a low protein diet (7% casein), levels of Lys supplementation ≥ 1.5% may exert adverse health effects in rats.

Iron profile and dietary pattern of primary school obese Egyptian children

Poor iron status affects billions of people worldwide. The prevalence of obesity continues to rise in both the developed and developing nations. An association between iron status and obesity has been described in children and adults. The aim of the study was to assess the iron profile and dietary pattern in primary school-aged obese Egyptian children. A case-control study was conducted on 120 children, both obese (n=60) and control group (n=60), recruited from three primary governmental schools located in Dokki Sector, El-Giza Governorate, Egypt. Their ages ranged from 6 to 12 years. All children were subjected to full medical and dietetic history, anthropometric measurements, thorough clinical examination, and determination of complete blood count, serum iron, total iron-binding capacity, transferrin saturation (TS), and ferritin. Despite similar dietary iron intake in the two groups, obese children showed highly significantly decreased hematocrit, mean corpuscular volume, mean corpuscular hemoglobin, serum iron, and TS, and increased mean corpuscular hemoglobin concentration and total iron-binding capacity when compared with the nonobese group. The obese group showed a highly significant increased rate of iron deficiency (ID) (TS<15% or mean corpuscular volume<76 fl) when compared with the nonobese group. Obesity was a significant risk factor for the development of ID (odds ratio: 7.09, 95% confidence interval: 3.16-15.92). The association between ID and obesity may have important public health and clinical implications. For primary school children with elevated BMIs, screening for ID should be considered. Increasing awareness of the importance of physical activity and carrying out nutritional education programs are required.

Biological Parameters Predictive Of Percent Dense Red Blood Cell Decrease Under Hydroxyurea Therapy

IntroductionDehydrated, dense red blood cells (DRBC), a subpopulation of sickle cells, are characterized by density >1.112; their increased mean corpuscular hemoglobin concentration (MCHC) leads to hemoglobin S (HbS) polymerization. The %DRBC is the biological parameter most strongly associated with some sickle-cell–disease (SCD) chronic organ damage, e.g., renal dysfunction, leg ulcers and priapism, also called hemolytic subphenotypes (Bartolucci et al. Blood 2012; Kato et al. Blood Rev 2007). Proven hydroxyurea (HU) efficacy against SCD lowers vaso-occlusive crisis, acute chest syndrome frequencies, and mortality (Charache et al. N Engl J Med 1995). The classical biological parameters indicating HU response are fetal hemoglobin (HbF) and mean corpuscular cell volume (MCV) increases (Steinberg et al. Blood 1997). However, we previously found decreased %DRBC in 33 patients after 6 months of HU (Bartolucci et al. Blood 2012) .We analyzed baseline biological parameters to identify those predictive of %DRBC decline under HU. Patients and methodsWe conducted a monocenter, prospective, longitudinal study on SCD patients undergoing HU therapy. Data were collected at baseline (day 0) and after 6 months of HU. Inclusion criteria were: SS and S-β0 thalassemia patients, age >18 years. Non-inclusion criteria were pregnancy, chronic blood transfusion and refused consent. Biological parameters determined were: %DRBC assessed with the phthalate density-distribution technique, D50 (defined as the density at which [(height of cells below phthalate index/sum of those above and below that index) = 0.5]), white blood-cell count (WBC count), MCV, MCHC, mean corpuscular hemoglobin content (MCH), total Hb, reticulocytes (RET), %HbF, platelet count, total bilirubin, alanine aminotransferase, aspartate aminotransferase, lactate dehydrogenase. Results are expressed as means ± SD, numbers or %, as appropriate. Quantitative parameters were compared between groups with Student's paired t-test. Correlations were established with Pearson's correlation coefficient. Multiple linear regressions were used to explore models that better predicted DRBC variation under HU. The final models included the variables that remained significantly associated with %DRBC decline after adjustment for the other variables in the models. R-squared (r2) were used as measures of variance explained by the models. P < 0.05 defined significance. This study was approved by the local Institutional Review Board. Results and DiscussionFifty-nine patients, mean age 35 ± 9 years, were included. Their %DRBC fell significantly by 40.7% after 6 months of HU therapy (P = 0.0003) from 10.1 ± 8% to 6 ± 4%. The %HbF rose from 7.2 ± 4% to 17.3 ± 8%. Our univariate analysis identified variables significantly correlated with %DRBC (Table). Multivariate analysis retained a significantly positive correlation between %DRBC decreases under HU and the pretreatment %DRBC on day 0. This statistical model accounted for 71.9% of the variability of %DRBC decline under HU. Pertinently, no correlation was found between %HbF and %DRBC changes, suggesting different mechanisms of action. ConclusionOur results confirmed the HU impact on %DRBC decrease, suggesting new indications to prevent or treat SCD complications associated with high %DRBC. They also showed that the major parameter predictive of DRBC decline under HU was the baseline %DRBC. %HbF and %DRBC changes under HU were not correlated. Prospective studies are needed to analyze the therapeutic effects of HU on chronic complications. Disclosures:No relevant conflicts of interest to declare.

A Divergent Artiodactyl MYADM-like Repeat Is Associated with Erythrocyte Traits and Weight of Lamb Weaned in Domestic Sheep

A genome-wide association study (GWAS) was performed to investigate seven red blood cell (RBC) phenotypes in over 500 domestic sheep (Ovis aries) from three breeds (Columbia, Polypay, and Rambouillet). A single nucleotide polymorphism (SNP) showed genome-wide significant association with increased mean corpuscular hemoglobin concentration (MCHC, P = 6.2×10−14) and genome-wide suggestive association with decreased mean corpuscular volume (MCV, P = 2.5×10−6). The ovine HapMap project found the same genomic region and the same peak SNP has been under extreme historical selective pressure, demonstrating the importance of this region for survival, reproduction, and/or artificially selected traits. We observed a large (>50 kb) variant haplotype sequence containing a full-length divergent artiodactyl MYADM-like repeat in strong linkage disequilibrium with the associated SNP. MYADM gene family members play roles in membrane organization and formation in myeloid cells. However, to our knowledge, no member of the MYADM gene family has been identified in development of morphologically variant RBCs. The specific RBC differences may be indicative of alterations in morphology. Additionally, erythrocytes with altered morphological structure often exhibit increased structural fragility, leading to increased RBC turnover and energy expenditure. The divergent artiodactyl MYADM-like repeat was also associated with increased ewe lifetime kilograms of lamb weaned (P = 2×10−4). This suggests selection for normal RBCs might increase lamb weights, although further validation is required before implementation in marker-assisted selection. These results provide clues to explain the strong selection on the artiodactyl MYADM-like repeat locus in sheep, and suggest MYADM family members may be important for RBC morphology in other mammals.

Preliminary acute and subchronic toxicity studies of GLG-V-13, a novel class III antiarrhythmic agent, in mice.

The acute and subchronic toxic effects of GLG-V-13 (3-[4-(1H-imidazol-1-yl)benzoyl]-7-isopropyl-3,7-diazabicyclo[3.3.1]nona ne dihydroperchlorate, CAS 155029-33-7), a novel class III with some class Ib antiarrhythmic activity, were investigated in mice. The estimated LD50 for GLG-V-13 given orally were 419 mg/kg for male mice and 383 mg/kg for female mice, respectively. The acute toxic signs appeared to be of the central nervous system in origin. Four groups of mice (15 per sex, group and dose) were fed daily with diets containing GLG-V-13 for 90 consecutive days. The equivalent daily doses were 0, 22, 50 and 121 mg/kg/day and 0, 27, 60 and 136 mg/kg/day for male and female mice, respectively. All of the mice survived. Food consumption was decreased. However, mean body weight and body weight gain were not significantly changed. Gross pathological changes, especially in the lungs and liver, were found in the middle and high dose groups. Consistent increased mean corpuscular hemoglobin concentration and decreased mean corpuscular hemoglobin were observed in all dose groups. Hepatocellular necrosis was found in both male and female mice treated with the drug and was dose-dependent. Marked vacuolation of the X zone in the adrenal gland with mild to moderate deposition of ceroid pigments (brown degeneration) was observed in female mice. Lesions in the kidneys and adrenal glands may be a possible reason for changes in serum sodium and potassium ions concentrations leading to an increase in water intake. A significant reduction in cholesterol in the high dose group may be a favorable pharmacological effect of GLG-V-13. The data from the 90-day subchronic toxicity studies indicate that GLG-V-13 appears to have limited systemic toxicity potential.

Relationships between oxidative stress markers and red blood cell characteristics in renal azotemic dogs

Oxidative stress parameters and erythrocyte characteristics were studied in 15 normal healthy dogs and 33 renal azotaemic dogs from Small Animal Hospital, Faculty of Veterinary Science, Chulalongkorn University. Dogs with renal azotaemia had reduced mean corpuscular volume (MCV) ( P < 0.01), packed cell volume (PCV) ( P < 0.001) and increased mean corpuscular hemoglobin concentration (MCHC) ( P < 0.001). The relationship was found between degree of azotaemia and MCV, PCV and MCHC. Dogs with severe renal azotaemia had higher intraerythrocytic sodium contents (RBC-Na) ( P < 0.05). The red blood cell catalase activity and glutathione and plasma malondialdehyde were unaltered while urinary malondialdehyde-creatinine ratio (U-MDA/Cr) increased significantly ( P < 0.001). The U-MDA/Cr was correlated significantly with plasma creatinine concentration ( P < 0.05), urinary protein-creatinine ratio ( P < 0.05) and fractional excretion of sodium ( P < 0.001). The results suggest some changes in RBC characteristics and urine oxidative stress marker in renal azotaemic dogs. Moreover, the U-MDA/Cr is a sensitive biochemical parameter which increased along with degree of renal dysfunction.

A comparison of anemia in hemoglobin C and normal hemoglobin A children with Plasmodium falciparum malaria

Plasmodium falciparum infection accelerates the senescence of erythrocytes. Senescence in hemoglobin C (HbC) erythrocytes relative to normal hemoglobin A (HbA) erythrocytes is also increased, presumably because of the sensitivity of HbC to oxidative damage and denaturation. To test for a possible increased rate of anemia in HbC individuals with malaria, we evaluated children with uncomplicated P. falciparum malaria in Bandiagara, Mali, a village with a high prevalence of HbC. The average hematocrit was significantly lower in AC children (heterozygous for HbC) than in AA children (homozygous for normal HbA). Calculated blood hemoglobin concentrations from these groups, however, showed no significant differences because of the increased mean corpuscular hemoglobin concentration (MCHC) and decreased mean corpuscular volume (MCV) of AC relative to AA erythrocytes. Average hemoglobin concentration is a better measure of oxygen delivery capacity and anemia than hematocrit value. By this measure, HbC, a malaria-protective polymorphism with few deleterious consequences, does not appear to be associated with more frequent anemia than normal HbA in episodes of uncomplicated P. falciparum malaria.

Genomewide Search for Dehydrated Hereditary Stomatocytosis (Hereditary Xerocytosis): Mapping of Locus to Chromosome 16 (16q23-qter)

Dehydrated hereditary stomatocytosis, also known as "hereditary xerocytosis," is caused by a red blood cell-membrane defect characterized by stomatocytic morphology, increased mean corpuscular hemoglobin concentration, decreased osmotic fragility, increased permeability to the univalent cations Na+ and K+, and an increased proportion of phosphatidylcholine in the membrane. The clinical presentation is heterogeneous, ranging from mild to moderate hemolytic anemia associated with scleral icterus, splenomegaly, and choletithiasis. Iron overload may develop later in life. The disease is transmitted as an autosomal dominant trait. We recruited a large three-generation Irish family affected with DHS and comprising 23 members, of whom 14 were affected and 9 were healthy. Two additional, small families also were included in the study. The DNA samples from the family members were used in a genomewide search to identify, by linkage analysis, the DHS locus. After the exclusion of a portion of the human genome, we obtained conclusive evidence for linkage of DHS to microsatellite markers on the long arm of chromosome 16 (16q23-q24). A maximum two-point LOD score of 6.62 at recombination fraction .00 was obtained with marker D16S520. There are no recombination events defining the telomeric limit of the region, which therefore is quite large. No candidate genes map to this area.

Sodium-potassium pump, ion fluxes, and cellular dehydration in sickle cell anemia.

We studied the role of the sodium-potassium pump in erythrocytes of 12 patients with sickle cell anemia (SS). Ouabain-binding sites per cell and pump-mediated Rb/K uptake were significantly higher in SS patients than in white or black controls. Ouabain-resistant Rb/K influx was also greater than in normal controls or patients with sickle cell trait. Deoxygenation of SS erythrocytes increased ouabain-sensitive Rb/K influx without altering ouabain binding, presumably as the consequence of an increase in the passive influx of sodium. Deoxygenation increased mean corpuscular hemoglobin concentration (MCHC) by 5.5%, and studies of the density distribution of SS cells indicated an increase in highly dense fractions known to contain sickled erythrocytes. Ouabain prevented the rise in MCHC and reduced the percentage of dense cells. These findings indicate a magnified role for the sodium-potassium pump in the pathophysiology of SS erythrocytes and suggest that its inhibition might prove useful in therapy.

Membrane-bound immunoglobulins and complement components on young and old red cells.

In order to characterize changes in membrane-bound immunoglobulins and complement components, red cells (RBCs) were separated into young and old populations by simple centrifugation. Old RBCs had reduced mean corpuscular hemoglobin volume, increased mean corpuscular hemoglobin concentration, and reduced sialic acid. Using radioactive anti-antiglobulin techniques, old RBCs were shown to have more IgG, IgM, IgA, and C3d on their surfaces than did young RBCs; there was no increase on old RBCs of C3b, factor B, C4b, or C5. Similar results were observed with RBCs strongly coated with C3d in vivo from a patient with cold agglutinin disease. RBCs taken into ethylenediamine tetraacetate, washed thoroughly in saline, and then stored for prolonged periods in Alsever's solution or kept in autologous ethylenediamine tetraacetate plasma, at 4 degrees C, showed no increase in RBC-bound C3d with increased storage time. If, however, blood was taken into citrate-phosphate-dextrose and maintained at 4 degrees C in autologous plasma, a significant increase in RBC-bound C3d was observed in the mixed-cell population with prolonged storage time. Order donor blood units, taken into citrate-phosphate-dextrose and stored at 4 degrees C as packed red cells, showed higher levels of RBC-bound C3d in the mixed-cell population than did units stored for a shorter time. In no case did donor unit RBCs give a positive direct antiglobulin test on serologic testing with anti-C3d. The findings complement data already collected on membrane and cytoplasmic changes in aging RBCs and may contribute to an understanding of RBC senescence.

Diagnosis of hereditary spherocytosis in newborn infants

The normal range of red blood cell osmotic fragility and autohemolysis was determined in venous blood of 32 healthy newborn infants. With these normal ranges as a reference, the diagnosis of hereditary spherocytosis was definitely possible in five newborn infants by demonstration of increased osmotic fragility of fresh and incubated red blood cells, moderately increased autohemolysis, and partial reduction of autohemolysis by the addition of glucose. Most previously studied newborn infants with hereditary spherocytosis have had atypical hyperbilirubinemia. Inconstant signs are anemia, reticulocytosis, erythroblastosis, spherocytes in the blood smear, and increased mean corpuscular hemoglobin concentration. In newborn infants with atypical hyperbilirubinemia in whom blood group incompatibilities are excluded, studies for hereditary spherocytosis should be done.

Effects of ultra-marathon training and racing on hematologic parameters and serum ferritin levels in well-trained athletes.

Hematologic parameters and serum ferritin levels were measured in groups of experienced ultra-marathon runners under control conditions, 2 days after a 160-km ultra-marathon, and for up to 14 days after a 56-km ultra-marathon. Under resting conditions, 14% of the runners had subnormal serum ferritin levels compared to 2% of a control group and not one of a group of trained swimmers. Serum ferritin levels that were markedly elevated after both ultra-marathon races returned to pre-race levels only 6 days after the 56-km ultra-marathon and continued to fall in athletes who did not exercise for a further 8 days. Other hematologic changes that were present after either of the ultra-marathon races included: immediate post-race hemoconcentration (shown by increased mean red cell count, hemoglobin level, and packed cell volume) and increased mean corpuscular volume, followed by hemodilution that was greatest 48 h after the 160-km race; an increased mean corpuscular hemoglobin concentration and reticulocyte production index; transient leukocytosis, monocytosis, lymphocytopenia, eosinophilopenia, and the appearance of band cells. With the exception of the increase reticulocyte production index and the reduced packed cell volume, all other hematologic parameters had returned to control levels 6 days after the 56-km race. This study shows that serum ferritin levels may be subnormal in a proportion of distance runners and that daily training and ultra-marathon racing in particular may cause these levels to remain elevated for between 6--14 days. Thus, when hematologic parameters are measured in distance runners, it should be remembered that recent prolonged exercise may (1) produce a "dilutional anemia," (2) by increasing serum ferritin levels, mask a true iron deficiency, and (3) that these changes may require up to 6 days to return to normal.

Cardiovascular correlates of maximal oxygen consumption rates in anuran amphibians

1. Maximal oxygen consumption rates (\(\dot V_{{\text{O}}_{\text{2}} } \) max; units, ml/g·h) were determined for four species of amphibians representing four families with habitat preferences varying from aquatic to terrestrial. Measured\(\dot V_{{\text{O}}_{\text{2}} } \) max were:Xenopus laevis (aquatic), 1.33±0.16;Rana pipiens (semi-terrestrial), 0.54±0.10;Bufo cognatus (terrestrial), 1.91±0.26; andScaphiopus couchii (terrestrial), 1.91±0.26. 2. In order to assess possible cardiovascular bases for these interspecific differences, heart rate increments (differences between resting and active heart rates) and ventricle weights were measured to evaluate differential cardiac outputs. In order to assess possible differential blood oxygen capacities, hematocrits and hemoglobin concentrations were measured. Blood volumes were determined to assess total blood oxygen storage capacities. 3. Ventricle weights were statisticaly significantly different (p S. couchii>X. laevis>R. pipiens. These differences were closely positively correlated with the maximal metabolic rates of the species (Fig. 3a). 4. There were no differences in heart rate increments between the four species (Fig. 2). 5. Blood oxygen capacities were directly correlated with hemoglobin concentrations (Fig. 1). There were no interspecific differences in the amounts of oxygen bound per gram of hemoglobin (1.3 ml O2/g Hb). Blood oxygen capacities were significantly different in the following sequence;X. laevis >S. couchii andB. cognatus>R. pipiens. 6. X. laevis had statistically significantly greater hematocrits than did the other three species.R. pipiens had significantly lower mean corpuscular hemoglobin concentrations. 7. Blood volumes were statistically significantly different between all species examined,S. couchii>B. cognatus>X. laevis>R. pipiens. 8. It is suggested that greater maximal oxygen consumption rates in anurans are correlated with 1) increased cardiac outputs based upon increased stroke volumes, 2) increased blood oxygen capacities due to either increased mean corpuscular hemoglobin concentration or increased hematocrit. Increased selective pressure for aerobic metabolism is also closely positively correlated with maximal blood oxygen storage capabilities.