Lack of prominent compensatory polycythemia in traditional native Andeans living at 4,200 meters

Red blood cell count (RBC), hemoglobin concentration ([Hb]) and hematocrit (Hct) were measured in 303 male Quechua children and adults, aged 6 to 57 years, living a lifestyle as traditional pastoralists and horticulturalists at a mean altitude of 4,200 m in the Southern Peruvian Andes. Values for RBC, [Hb], and Hct increased with age from middle childhood to young adulthood. However, among adults there was no significant association between age and any of these three parameters. Overall, there was approximately a 10-12% increase in the RBC, [Hb], and Hct above sea-level norms for all age groups. Mean corpuscular volume (MCV) and mean corpuscular hemoglobin (MCH) showed a slight but significant increase with age in children and adolescents, but the mean corpuscular hemoglobin concentration (MCHC) did not. We conclude that the study of highland Quechua Indians, living a traditional lifestyle as pastoralists and horticulturalists, does not support the long-held belief that altitude hypoxia provokes a dramatic compensatory polycythemia in healthy Andeans.     

Mature hematology in neonatal walruses supports diving alongside their mothers

An animal's physiology limits the environmental conditions where it can persist; quantifying the physiology of the walrus is timely since they are being impacted by alterations in sea ice. We examined postnatal changes in hematology, an important attribute that supports diving, by analyzing a longitudinal data set from aquaria walruses (five males and nine females) sampled from 0.04 to 12.0 years of age (n = 795 samples). Red blood cell count (RBC), hemoglobin (Hb), hematocrit (Hct), mean corpuscular volume (MCV), mean cell hemoglobin (MCH), and mean corpuscular hemoglobin content (MCHC) did not change markedly after birth and appears to have not been influenced by sex. Estimated values at birth were RBC: 3.78 ± 0.12 × 10⁶ mm⁻³, Hb: 17.62 ± 0.82 g dl⁻¹, Hct: 45.21 ± 2.01%, MCV: 118.99 ± 3.99 fl, MCH: 47.10 ± 1.77 pg, and MCHC: 39.60 ± 0.70 g dl⁻¹. Compared to newborns, there were only subtle decreases in RBC, Hb, and MCHC, and a slight increase in MCV in the years following birth; Hct and MCH appear not to have changed. Unlike other pinnipeds, walruses swim within days of birth and have a prolonged 2-year nursing interval. Mature hematology early in life supports breath-holding, as young walruses must transit under sea ice with patchily distributed breathing holes.     

Cadmium induced MTs synthesis via oxidative stress in yeast Saccharomyces cerevisiae

Lignan complex has been isolated from flaxseed. It has been shown to reduce serum lipids and the extent of hypercholesterolemic atherosclerosis. However, it is not known whether the chronic use of lignan complex has any adverse effects on the hemopoietic system. The effects of lignan complex (40 mg/kg body wt orally daily for 2 months) on the red blood cells (RBC) count, mean corpuscular volume (MCV), red cell distribution width (RDW), hematocrit (Hct), hemoglobin (Hb), mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentration (MCHC), and counts of white blood cell (WBC), granulocytes, lymphocytes, monocytes and platelet, and platelet volume were investigated in normo- and hypercholesterolemic rabbits. The results show that lignan complex had no adverse effects of counts of RBC, WBC, granulocytes, lymphocytes, monocytes and platelet in both the normo- and hyper-cholesterolemic rabbits. The values for MCV, RDW, Hct, Hb, MCH, MCHC, and platelet volume were similar in lignan complex-treated or untreated normo- and hypercholesterolemic rabbits. It is concluded that chronic use of lignan complex had no adverse effects on the hemopoietic system. (Mol Cell Biochem 270: 139–145, 2005)     

Hematological responses to thermal acclimation in a cold water squaliform (Heterodontus francisci girard)

Summary The hematological modifications occurring as a result of acclimation to increased temperature in the cold water horn shark,Heterodontus francisci, were evaluated. Sharks were maintained under constant conditions except for temperature (15°C and 25°C) in a closed marine system. The total red blood cell (RBC) number decreased in the 25°C sharks. In contrast, hemoglobin concentration, hematocrit, mean corpuscular volume (MCV) and mean corpuscular hemoglobin (MCH) significantly increased at 25°C compared to the control animals. RBC size was increased at 25°C, but the surface area/mm³ whole blood was reduced. Folic acid levels were not different between the groups. Vitamin B₁₂ levels decreased and testosterone increased at 25°C. Blood pH, number of erythroblasts, number of white blood cells (WBC) and WBC differential analyses were essentially unchanged at the two temperatures, except that the relative neutrophil number was increased. The major hematological changes occur in the erythrocytes and appear to be sequential in nature with an initial loss of RBC followed by increased hemoglobin synthesis and increased RBC size, but lack of recovery of RBC numbers.Abbreviations Hb hemoglobin - Hct hematocrit - MCH(C) mean corpuscular hemoglobin (concentration) - MCV mean corpuscular volume - RBC red blood cells - WBC white blood cells Contribution Number 359, Department of Biology     

Effect of chronic administration of vitamin E on the hemopoietic system in hypercholesterolemia

Hypercholesterolemia induces oxidative stress, which is known to have adverse effects on the integrity of cells. Hence, hypercholesterolemia may have adverse effects on the hemopoietic system. Vitamin E, an antioxidant, is being used by normo- and hypercholesterolemic subjects. It is, however, not known if vitamin E has any beneficial or adverse effects on the hemopoietic system. The objectives of this study are to determine if (i) hypercholesterolemia has any adverse effects on the hemopoietic system [red blood cell (RBC) count, mean corpuscular volume (MCV), red blood cell distribution width (RDW), hematocrit (Hct), hemoglobin (Hb), mean corpuscular hemoglobin (MCH), MCH concentration (MCHC), white blood cell (WBC), and platelet counts, and mean platelet volume (MPV)], and (ii) vitamin E has any effect on the hemopoietic system in hypercholesterolemia. Blood samples were collected before and at various intervals during a high cholesterol diet (0.25% cholesterol) for 2 and 4 months, and while on high cholesterol diet with vitamin E (2 months) following a high cholesterol diet (2 months). Serum cholesterol was measured on an automated Clinical System Analyzer and hemopoietic parameters were measured on an automated Cell-dyn-4000. The results show that hypercholesterolemia decreased RBC count, Hct and Hb, increased MCV, RDW, MCH, and MCHC, and had no effect on WBC and platelet counts, and MPV. Vitamin E did not affect any of the parameters of the hemopoietic system. In conclusion, hypercholesterolemia of short duration has adverse effects on certain elements of the hemopoietic system. Vitamin E does not affect the hemopoietic system during hypercholesterolemia.     

Effect of triploidy on turbot haematology

This study was carried out to compare key haematological features of diploid (2n) and triploid (3n) turbot as a first step towards the assessment of the ability of 3n turbot to withstand sub-optimal culture conditions. Morphometric indices of erythrocytes were determined on blood smears by light microscopy. Triploidy significantly (P<0.001) increased all morphometric indices measured in the erythrocytes, including size, surface, and volume, except for the size of minor nuclear axis. The increase in cell size was larger for the major (31.0%) than for the minor (8.3%) axis, thus rendering erythrocytes of 3n turbot more ellipsoidal. The increase in erythrocyte volume (45.9%) was close to the theoretical expected 50% increase as a result of one extra chromosome set. Haematological indices were measured automatically by a haematological Coulter Counter. Triploid turbot had lower numbers of red blood cells (RBC: 1.84 cells pL(-1) in 2n vs. 1.27 cells pL(-1) in 3n; P<0.001) but they were of a larger size (Mean corpuscular volume [MCV]: 145.51 fL in 2n vs. 181.78 fL in 3n; P<0.001). However, the decrease in RBC was not compensated by the increase in MCV, and thus, triploidy decreased the haematocrit (Hct: 26.80% in 2n vs. 23.11% in 3n; P<0.001) and total blood haemoglobin concentration (Hb: 73.74 g l(-1) in 2n vs. 67.54 g l(-1) in 3n; P<0.05). In contrast, mean corpuscular hemoglobin (MCH: 40.27 pg in 2n vs. 53.28 pg in 3n; P<0.001) was higher for 3n turbot as a result of their larger erythrocytes although MCH concentration (MCHC: 0.28 pg fL(-1) in 2n vs. 0.29 pg fL(-1) in 3n did not significantly differ. RBC, Hct and MCV were also determined manually using light microscopy. In general, discrepancies between the two methods were small (overall approximately 7%) but the Coulter Counter tended to overestimate RBC and Hct (and thus to underestimate MCV). Nevertheless, relative differences between ploidies were very similar, thus verifying triploidy-associated changes in hematological features. These changes, as determined in the present study, are essential when evaluating the feasibility of triploid turbot for intensive aquaculture systems in which unfavorable situations may occur.     

The effect of different dietary iron levels on growth and hepatic iron concentration in juvenile gibel carp (Carassius auratus gibelio)

An 83-day growth trial was conducted using a flow-through system to examine the effects of different dietary iron levels on growth and hepatic iron concentration in juvenile gibel carp ( Carassius auratus gibelio ). Six purified diets supplemented with different levels of iron (0, 10, 30, 60, 100 and 200 mg kg⁻¹) (as ferrous sulfate) were fed to triplicate groups of fish (initial weight 2.12 ± 0.00 g per fish). The results showed that the addition of iron to the basal diet did not significantly affect the specific growth rate (SGR), feed efficiency (FE), survival, red blood cell amount (RBC), hemoglobin content (Hb), mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH) or mean corpuscular hemoglobin concentration (MCHC). Hepatic iron concentration and hematocrit (Hct) were significantly influenced by dietary iron level (P < 0.05). On the basis of the iron concentration for the maintenance of optimum hepatic iron concentration and Hct, it was concluded that the dietary iron concentration of juvenile gibel carp should be not less than 202 mg Fe kg⁻¹ diet.     

Effect of irradiation and/or leucocyte filtration on RBC storage lesions

Red blood cell (RBC) storage lesions have been shown to be associated with some adverse reactions; numerous studies have focused on the lesions caused by storage, and few data on the RBC storage lesions caused by prestorage treatments of leucocyte filtration and irradiation. In this study, we examined the changes related with the RBC storage lesions, including 2,3-diphosphatidylglyceric acid (2,3-DPG), pH, free hemoglobin (Hb), supernatant free K+ and Na+ concentration, mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH). Along with the increasing storage time, decreases in 2, 3-DPG levels, pH and Na+ concentration, increases in K+ and free Hb concentrations, and significant morphological changes in RBC in all groups were found. The changes in the groups of irradiation, leucocyte filtration and the combined irradiation and leucocyte filtration were more significant than those in the untreated group. Meanwhile, the MCV levels of the three treated groups were significantly lower than those in the untreated group, while the MCH variations were significantly higher. Our results suggest that irradiation and leucocyte filtration before storage may aggravate blood storage lesions.     

Changes in hematological parameters in free-living pigeons (Columba livia f. urbana) during the breeding cycle

The blood parameters—red blood cell (RBC) count, hematocrit (Ht), hemoglobin concentration (Hb), mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), and mean corpuscular hemoglobin concentration (MCHC)—were studied for the first time in free ranging pigeons Columba livia f. urbana. The aim of the study was to establish a set of reference values for this ubiquitous urban species and to examine a potential influence of the factors such as sex and phase of the breeding cycle on the hematological parameters. Blood was sampled from the adult individuals of both sexes during the breeding cycle. Significant variations in Ht and Hb were observed, while RBC count remained unchanged. The lower hematocrit value and hemoglobin concentration found in both males and females during molt probably resulted from the increase of plasma volume not accompanied by an increase in RBC. On the other hand, a significant physiological stress of nutritional deficiency during this energy-consuming stage may manifest itself in the decreased Ht and Hb values. The higher values of Ht and Hb during the laying phase could be related to the dehydration status. There were no overall differences in MCV, MCH, and MCHC values in either of the breeding stage. A lack of sex dimorphism in the measured and calculated blood parameters was apparent. Data collected herein contribute to the better understanding of general physiology of the ubiquitous urban species. The knowledge of variation in the blood indexes with respect to sex and breeding stage is crucial before blood parameters can provide an useful information on physical condition of the bird.     

Haematological profile of common carp spawners of various breeds

The goal of this study was to determine the basic haematological profile of common carp (Cyprinus carpio L.) spawners of eight breeds reared under identical conditions and sampled in spring after overwintering. Significant differences were found among the breeds for haemoglobin level (Hb), haematocrit value (PCV), mean corpuscular volume (MCV) and mean corpuscular haemoglobin (MCH) values. The number of red blood cells (RBC), mean corpuscular haemoglobin concentration (MCHC), number of leukocytes (WBC) and leukocyte differential count (WBC DIFF) did not differ significantly among the respective breeds. The highest Hb, PCV and MCH values were found for Ropsha scaly carp (ROP) and Amur wild carp (AS) (Hb 109 ± 17 and 106 ± 15 g l^?1; PCV 0.40 ± 0.06 and 0.40 ± 0.06 l l^?1; MCH 69 ± 7 and 69 ± 9 pg, respectively). The AS specimens and breeds that originated [ROP, Ukraine scaly carp (US), and Northern mirror carp (M72)] showed significantly higher values of Hb (P < 0.01), PCV (P < 0.01), MCV (P < 0.05) and MCH (P < 0.05), compared to the other four breeds: Hungarian mirror carp (M2), Israeli mirror carp (Dor 70), South Bohemian mirror carp (BV) and Tata scaly carp (TAT). Males showed significantly higher PCV, Hb and RBC values within individual breeds. This study demonstrated that Amur wild carp and breeds originating from it had significantly higher values of erythrocyte profile in comparison with the other breeds studied.     

Age and gender related changes in hematological parameters of thoroughbred foals

Abstract

Hematological and biochemical profiles commonly are required in equine medicine. We studied hematological parameters including red blood cells (RBC), white blood cells (WBC), hemoglobin (Hb), hematocrit (PCV), differential leukocyte counts, mean cell volume (MCV), mean corpuscular hemoglobin (MCH), and mean corpuscular hemoglobin concentration (MCHC) in thoroughbred foals at different ages and for both sexes. Sixty healthy thoroughbred foals, 1 day, 3 days and 1 year old were used. Each age group consisted of 10 male and 10 female animals. We found significant differences related to age in RBC values of females, PCV, MCV values of males, WBC, neutrophil percentages, lymphocyte percentages, monocyte percentages of females, and eosinophil percentages and basophil percentages. Significant differences related to gender were found only with regard to PCV at 1 year and WBC at 1 day. The hematological parameters of thoroughbred foals up to one year old may be useful for evaluating and monitoring the health of these animals.     

Quantitative trait loci for baseline erythroid traits

A substantial genetic contribution underlies variation in baseline peripheral blood counts. We performed quantitative trait locus/loci (QTL) analyses to identify chromosome (Chr) regions harboring genes influencing the baseline erythroid parameters in F₂ intercrosses between NZW/LacJ, SM/J, and C57BLKS/J inbred mice. We identified multiple significant QTL for red blood cell (RBC) count, hemoglobin (Hgb) and hematocrit (Hct) levels, mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), and mean cell hemoglobin concentration (CHCM). We identified four RBC count QTL: Rbcq1 (Chr 1, peak LOD score at 62 cM,), Rbcq2 (Chr 4, 60 cM), Rbcq3 (Chr 11, 34 cM), and Rbcq4 (Chr 10, 60 cM). Three MCV QTL were identified: Mcvq1 (Chr 7, 30 cM), Mvcq2 (Chr 11, 6 cM), and Mcvq3 (Chr 10, 60 cM). Single significant loci for Hgb (Hgbq1, Chr 16, 32 cM), Hct (Hctq1, Chr 3, 42 cM), and MCH (Mchq1, Chr 10, 60 cM) were identified. The data support the existence of a common RBC/MCH/MCV locus on Chr 10. Two QTL for CHCM (Chcmq1, Chr 2, 48 cM; Chcmq2, Chr 9, 44 cM) and an interaction between Chcmq2 with a locus on Chr 19 were identified. These analyses emphasize the genetic complexity underlying the regulation of erythroid peripheral blood traits in normal populations and suggest that genes not previously recognized as significantly impacting normal erythropoiesis exist.     

Quantitative trait loci for porcine baseline erythroid traits at three growth ages in a White Duroc × Erhualian F<Subscript>2</Subscript> resource population

Baseline erythroid indices are increasingly involved as risk factors for common complex diseases in humans. However, little is known about the genetic architecture of baseline erythroid traits in pigs. In this study, hematocrit (Hct), hemoglobin (Hgb), mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentration (MCHC), mean corpuscular volume (MCV), red blood cell (RBC), and red cell distribution width (RDW) were measured in 1420 (day 18), 1410 (day 46), and 1033 (day 240) F(2) pigs from a White Duroc x Erhualian intercross resource population. The entire resource population was genotyped for 183 microsatellite loci across the pig genome, and the quantitative trait loci (QTL) analysis was performed for all erythroid-related traits measured with QTL Express based on a least-squares method. A total of 101 QTL, including 46 genome-wide significant QTL and 55 chromosome-wide significant QTL, regulating erythroid traits were found on all pig chromosomes (SSC) except for SSC15 and SSC18. The genome-wide significant QTL were mainly localized on SSC1, 7, 8, 10, and X. These results confirmed most of QTL previously identified in the swine. More importantly, this study detected age-specific QTL for baseline erythroid traits in pigs for the first time. Notably, the QTL for MCV and MCH on day 18 on SSC8 with small intervals of 3 and 4 cM, respectively, provided a good starting point for identifying causal genes underlying MCV and MCH in the future.     

Haematological studies on the prewintering and wintering frog, Rana esculenta

1. A study of the haematology of the frog Rana esculenta including erythrocyte count (RBC), haemoglobin content (Hb), haematocrit (HCT), mean cell volume (MCV), mean corpuscular haemoglobin (MCH), mean corpuscular haemoglobin concentration (MCHC) and erythrocyte size as a function of prewinter and winter was made. 2. The RBC count and Hb were significantly higher in contrast to MCV and MCH values during prewinter in both sexes. 3. The surface area to volume ratio was higher in prewinter whereas the length to width ratio (eccentricity) of the cytosome and nucleus was significantly higher during winter in both sexes. 4. Sexual differences in the erythrocyte count, Hb content and the surface area to volume ratio were also observed. 5. The physiological significance of these observations are reported for Rana esculenta.     

甘肃鼢鼠血象及其与低氧适应的关系

甘肃鼢鼠(Myospalax cansus)是一种严格营地下生活的鼠类,其形态、行为及生理特征均与地面鼠不同。为探讨甘肃鼢鼠适应低氧环境的机理,本研究采用血象指标测定方法,对甘肃鼢鼠低氧适应前后的红细胞数、血红蛋白浓度、红细胞压积等各血象指标进行测定。结果显示,甘肃鼢鼠低氧适应后红细胞数、血红蛋白浓度和红细胞压积均显著升高,而平均红细胞体积、平均红细胞血红蛋白及平均红细胞血红蛋白浓度明显下降。与地面生活的啮齿动物低氧适应后血象相比,甘肃鼢鼠红细胞数量多,红细胞压积大,血红蛋白浓度高,红细胞膜表面积大,血红蛋白的利用率较高,可能是对低氧环境适应的一种途径。     

Normal hematological values of the African neonate

A longitudinal study of normal hematological values of the newborn infant was undertaken in an effort to provide baseline data for assessing the African Neonate with hematological problems. There were 402 neonates, consisting of 304 full-term, 51 preterm and 47 post-term infants. The Hematocrit (Hct), Hemoglobin (Hb), Red Blood Cell Count (RBC), Reticulocyte count (Retic) and Nucleated Red Blood Cell Count (NRBC) were serially determined. The red cell indices, Mean corpuscular Hemoglobin (MCH), Mean Corpuscular volume (MCV) and Mean corpuscular Hemoglobin Concentration (MCHC) were calculated for each neonate. Our results showed that African neonates have lower hematological values than their North American and European counterparts. This was neither a reflection of an intrauterine anemia nor was it due to variables resulting from the timing of cord blood sampling. On the first day of life, the mean Hct was 45.4%; mean Hb was 15.46 gm/dl; and the RBC was 4.02 X 10(6) cells/mm2. The Retics, NRBC and other red blood cell indices do not differ from those of neonates reported from other parts of the world. We suggest therefore that the low hematological values of the African neonate may be intrinsic.     

Testosterone action on erythropoiesis does not require its aromatization to estrogen: Insights from the testosterone and estrogen treatment of two aromatase-deficient men

Androgens act on erythropoiesis, but the relative role of testosterone (T) and estradiol (E₂) on erythropoietic parameters in men is a poorly investigated issue. In order to evaluate separately the effects on erythropoiesis of high-dose T administration alone and of physiological dose of E₂ administration alone two adult men with aromatase deficiency were assessed before and during each treatment. Blood cell count, hemoglobin (Hb), hematocrit (Hct), erythrocyte mean cell volume (MCV), erythrocyte mean corpuscular hemoglobin (MCH), erythrocyte mean corpuscular hemoglobin concentration (MCHC), serum ferritin, iron and total iron-binding capacity (TIBC), serum erythropoietin, serum total testosterone and estradiol were evaluated. Hb, Hct and red cell count rose during testosterone treatment, consistently with the increase in circulating testosterone, but failed to increase during estradiol treatment. A decrease in Hb, Hct and red cell count was recorded in one of the two subjects during estradiol treatment, with a concomitant decrease in serum testosterone. Circulating T alone is capable of and sufficient to influence erythropoiesis, especially at supraphysiological dosage, while circulating E₂ have not the same effect on erythropoietic parameters, suggesting the hypothesis that the erythropoietic changes induced by androgens are not mediated via its aromatization to estrogens.     

Blood parameter changes during stopover in a long-distance migratory shorebird, the bar-tailed godwit Limosa lapponica taymyrensis

Bar-tailed godwits migrate from West African wintering sites to breeding areas in northern Russia with only one stopover. We compared hematocrit (Hct), blood hemoglobin concentration (Hb), and mean cell hemoglobin concentration (MCHb; a measure of the relative proportion of Hb in the cellular blood fraction) between arriving godwits lured to land 60 km short of the stopover site and godwits during subsequent refueling. The Hct and Hb of arriving godwits was low when compared to that of refueling birds. On the stopover site, Hct and Hb correlated positively with size-corrected body mass. In addition, Hb and MCHb reached peak levels in the last days of stopover. We explored the possibility of regenerative anemia in arriving godwits by comparing the fraction of reticulocytes (young red blood cells) between arriving and refueling birds. No differences were found. Therefore, we suggest that the increase in Hct, Hb, and MCHb during refueling is not in response to a severe anemic state at arrival. Rather, we suggest that the increase in blood parameters may anticipate the increased aerobic requirements of impending migratory flight and possibly satisfy heightened oxygen demands of the larger body mass of fattened birds. The Hct increase on the stopover site may also serve to buffer the red blood cell population against possible red blood cell breakdown during long-distance flight.     

Effect of storage time on haematological parameters in mullet,Mugil cephalus

The aim of the present study was to assess the effect of storage time at +4 °C on red blood cell count (RBC), haematocrit (Hct), haemoglobin (Hb), white blood cell count (WBC), thrombocyte count (TC), mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH) and mean corpuscular hemoglobin concentration (MCHC) in mullet (Mugil cephalus) using an automatic method. After blood collection (T₀), all samples were analyzed using both the manual and automatic method. To test the validation of the automatic method, a paired t‐test was applied, and no statistical difference was observed. The samples were successively divided into four different aliquots and stored at +4 °C to assess the haematological parameters using the automatic method. The first aliquot was refrigerated for 6 h, the second one for 24 h, the third one for 48 h and the last one at for 72 h. One‐way repeated‐measures ANOVA showed a significant effect of storage time (P < 0.05) on Hb, WBC, TC, MCH and MCHC. These results suggest that haematological parameters can be assessed within 6 h from blood collection when samples are stored at +4 °C because long‐term storage modifies the results of the analyses. Further studies on these parameters could be still needed in various fish species to validate an appropriate method for haematological analysis useful not only for the evaluation of the health status of animal living in captivity and in aquaculture but also to have reliability environmental haematological biomarkers. Copyright © 2012 John Wiley & Sons, Ltd.     

Response of red cell and plasma volume to prolonged training in humans

To clarify the role of progressive heavy training on vascular volumes and hematologic status, seven untrained males [maximal O2 uptake (VO2max) = 45.1 +/- 1.1 (SE) ml.kg-1.min-1] cycled 2 h/day at an estimated 62% of VO2max. Training was conducted five to six times per week for approximately 8 wk. During this time, VO2max increased (P less than 0.05) by 17.2%. Plasma volume (PV) measured by 125I increased (P less than 0.05) from 3,068 +/- 104 ml at 0 wk to 3,490 +/- 126 ml at 4 wk and then plateaued during the remaining four wk (3,362 +/- 113 ml). Red cell (RBC) mass (RCM) measured by 51Cr-labeled RBC did not change during the initial 4 wk of training (2,247 +/- 66 vs. 2,309 +/- 128 ml). As well, no apparent change occurred in RCM during the final 4 wk of training when RCM was estimated using PV and hematocrit (Hct). Collectively, PV plus RCM, expressed as total blood volume (TBV), increased (P less than 0.05) by 10% at 4 wk and then stabilized for the final 4 wk. During the initial phase of training, reductions (P less than 0.05) were also noted in Hct (4.6%), hemoglobin (Hb, 4.0%), and RBC count (6.3%). In contrast, an increase in mean cell volume (MCV, 1.7%) and mean cell Hb (2.3%) was observed (P less than 0.05). From 4 to 8 wk, no further changes (P greater than 0.05) in Hb, RBC, and MCV were found, whereas both mean cell Hb and Hct returned to pretraining levels.(ABSTRACT TRUNCATED AT 250 WORDS)