首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 31 毫秒
1.
D B?ning  G Enciso 《Blut》1987,54(6):361-368
In blood of 21 anemic patients and 8 normal subjects (N) three oxygen dissociation curves each were measured at different pH values to calculate Bohr coefficients after acidification with CO2 (BCCO2) or fixed acid (BCFA), and other important parameters of oxygen affinity. The patients had either low hemoglobin or red cell production (L: n = 11, 7.3 g/dl Hb) or high erythrocyte production combined with high loss (H: n = 10, 7.8 g/dl Hb). The standard half saturation pressure P50 (pH 7.4, 37 degrees C) was equally elevated in both anemic groups (L: 30.5, H: 30.8, N: 26.7 mmHg), as well as the diphosphoglycerate concentration (DPG) (L: 18.7, H: 18.6, N: 12.7 mumol/g Hb). The red cell pH of the anemics was lower than for the N (approximately 0.045 units) causing part of the difference in P50. Hill's "n" tended to high values in the anemics except at low O2-saturation in the H. For BCCO2 no significant difference among the groups was observed. BCFA, however, increased in the H at low SO2 compared to the N and L. The cause for most of the changes in hemoglobin oxygen affinity in anemics was the high [DPG]. The combination of high P50 and high "n" value as in the L seems to be most advantageous for tissue oxygenation.  相似文献   

2.
Eleven male sport students (age 23.3 +/- 1.7 years) exercised for 2 h on a bicycle ergometer (60 rpm), the braking force of which was regulated to yield a constant pulse rate (156 +/- 3 min-1). Before, at end of, and 3 and 6 h after exercise blood was sampled from a cubital vein and an earlobe for measurement of hemoglobin (Hb) concentration, hematocrit (Hct) value, osmolality (Osm), plasma protein (Prot), sodium (Na+), potassium (K+), inorganic phosphate (Pi), and lactate (Lac) concentrations, red cell 2,3-diphosphoglycerate (DPG) and adenosin triphosphate (ATP) concentrations, acid base status and half saturation pressure (P50) of the oxygen dissociation curve. At end of exercise [Hb], Hct, [Prot], Osm, [K+], [Pi] and [Lac] were significantly elevated, pH in ear lobe (+ 0.04) and venous blood (+ 0.08) was also increased by both respiratory and nonrespiratory effects (BE + 1.4 mmol/l). The oxygen dissociation curve showed an unexplained slight right shift (standard P50 + 0.19 kPa). During the post-exercise period most parameters approximated to control values after only 3 h. [Prot] and especially [Pi], however, remained elevated while [DPG] slightly rose during the post-exercise period. It is suggested that these changes are first signs of adaptation to exercise, perhaps caused by endocrine stimulation.  相似文献   

3.
The diffusion coefficient (D) of 2,3-bisphosphoglycerate (DPG) was measured using pulsed-field gradient (PFG)-31P nuclear magnetic resonance spectroscopy in solutions containing 2.7-5.0 mM hemoglobin (Hb) and a range of DPG concentrations. The dependence of the measured values of D on the fraction of the total DPG in the sample that is bound to Hb enabled the estimation of the dissociation constants (Kd) of complexes of DPG with carbonmonoxygenated, oxygenated, and deoxygenated Hb; the values of Kd (mM), measured at 25 degrees C, pH 6.9 and in 100 mM bis Tris/50 mM KCl, were 1.98 +/- 0.26, 1.8 +/- 0.5 and 0.39 +/- 0.26, respectively. In intact erythrocytes the apparent diffusion coefficient, Dapp, of DPG was larger in oxygenated and carbonmonoxygenated cells (6.17 +/- 0.20 x 10(-11) m2s-1) than in deoxygenated cells (4.10 +/- 0.23 x 10(-11) m2s-1). Changes in intracellular DPG concentration (5-55 mM) in erythrocytes, brought about by incubation in a medium containing inosine and pyruvate, did not result in significant changes in the value of Dapp; this result supports the hypothesis that DPG binds to other sites in the erythrocyte. Monte Carlo simulations of diffusion in biconcave discs were used to test the adequacy of the values of Kd estimated in solution to describe the binding of DPG to Hb in oxygenated and deoxygenated erythrocytes. The results of the simulations implied that the value of Kd estimated for deoxygenated Hb-DPG was greater than expected from the experiments involving intact erythrocytes. This difference is surmised to be at least partly due to the difficulty of measuring D at low-ligand concentrations. Notwithstanding this shortcoming, the PFG method appears to be suitable for probing interactions between macromolecules and ligands when the Kd is in the millimolar range. It is one of the few techniques available in which these interactions can be studied in intact cells. In addition, the Monte Carlo simulations of the diffusion experiments highlighted important differences between theory and experiment relating to the nature of molecular motion inside the cells.  相似文献   

4.
The carriage of oxygen by the blood and the in vivo response of the brain were investigated in mice infected with a lethal strain of Plasmodium yoelii. All mice with parasitaemia exceeding 70% were severely anaemic (Hb 3.5 +/- 1.8 g/dl; mean +/- 1 SD), acidotic (blood pH 7.04 +/- 0.06) and hypoglycaemic (blood glucose 0.6 +/- 0.76 mumol/ml). The oxyhaemoglobin dissociation curve (ODC) of blood from heavily infected mice was shifted right as compared to controls, but the increase in p50 was less than expected from the accompanying acidosis. The reduced shift right was due to a decrease in the 2,3-DPG/Hb ratio in infected animals (0.72 +/- 0.12, n = 17 vs 1.10 +/- 0.09, n = 12 in controls). Despite the severity of terminal infection, the cerebral pH and the relative steady-state concentrations of PCr, ATP and Pi measured in vivo by nuclear magnetic resonance (31P NMR) were normal. Alterations in brain energy status and pH cannot account for cerebral signs or death in this proposed mouse model of cerebral malaria.  相似文献   

5.
Oxygen affinity and other hematological parameters in strictly subterranean mole-rats, Cryptomys hottentotus (subspecies pretoriae) were measured immediately upon capture and after 14-21 days in captivity. The pH, hematocrit, hemoglobin (Hb) concentration, blood oxygen content, 2,3 bisphosphoglycerate (2,3 BPG) concentration and oxygen dissociation curves (ODC), as well as tonometric measurements, were determined using whole blood. Additionally ODCs were also determined for stripped hemolysates of individual animals. Compared to other mammals, blood of freshly caught animals had low pH (7.32+/-0.22), elevated hematocrits (48.4+/-3.8 %) and significantly lower P50 values for whole blood (21.1+/-1.6 mm Hg at pH 7.4) than those reported for other similar-sized fossorial and terrestrial mammals. Blood carbon dioxide content (22.4+/-3.9 mMol L(-1)), hemoglobin concentration (1.9+/-0.15 mMol L(-1)), oxygen content (164.8+/-26 mL L(-1)), bicarbonate concentrations (22.5+/-3.5 mMol L(-1)) were within the range of values reported for similar-sized mammals. We conclude that high blood-oxygen affinity, low body temperature and possibly also high hematocrit enable C. h. pretoriae to maintain an adequate oxygen supply to the tissues in a potentially hypoxic burrow atmospheres, but that the blood of this species shows no exceptional CO2 sensitivity or buffering capacity.  相似文献   

6.
Hemoglobin Attleboro, a new alpha-chain variant with a substitution of proline for serine at position 138 (H21), was found to be a noncooperative high-affinity hemoglobin (P50 = 0.26 mmHg at pH 7 and 20 degrees C) which lacked an alkaline Bohr effect. Addition of 2,3-diphosphoglycerate (DPG) or inositol hexaphosphate (IHP) led to a decrease in oxygen affinity but to no alteration in either Bohr effect or cooperativity. Ligand binding kinetics studies revealed an overall rate of oxygen dissociation at pH 7.0 and 20 degrees C that was 2.7-fold slower than that for Hb A. At pH 8.5, the kinetic profile was identical with that at pH 7, confirming the absence of a Bohr effect for this variant hemoglobin. Measurement of the rate of oxygen dissociation with carbon monoxide replacement indicated a lack of cooperativity. Sedimentation velocity experiments yielded s20,w values of 2.8 and 4.3 for 65 microM solutions of oxyhemoglobins Attleboro and A, respectively (indicating an enhancement in the oxy dimer population of this variant). Studies of the carbon monoxide combination of this variant revealed an association rate 20-fold faster than that for Hb A; only in the presence of a 1000-fold molar excess of IHP was there a significant reduction in the overall rate. Rapid-scan and traditional stopped-flow experiments conducted in the Soret Soret region demonstrated an alteration in the structure and rate of assembly of the deoxy tetramer of Hb Attleboro relative to that of Hb A. The abnormal properties of this hemoglobin variant can be attributed to major perturbations in the C-terminal region.  相似文献   

7.
Oxygen dissociation curves (ODC) in whole blood and organic phosphate concentrations in red cells were determined in 10 highly trained male athletes (TR), 6 semitrained subjects (ST) who played sports regularly at low intensities and 8 untrained people (UT). In all groups standard ODCs (37 degrees C, pH 7.40, PCO2 approximately 43 Torr) at rest and after a short exhaustive exercise were nearly identical, but PO2 values measured immediately after blood sampling and corrected to standard conditions tended to fall to the right of the in vitro ODC. Elevated P50 in the physically active [28.65 +/- 1.4 Torr (3.81 +/- 0.18 kPa) in ST, 28.0 +/- 1.1 Torr (3.73 +/- 0.15 kPa) in TR, but 26.5 +/- 1.1 Torr (3.53 +/- 0.15 kPa) in UT] were partly caused by different [DPG] (11.9 +/- 1.3 mumol/GHb in UT, 13.3 +/- 1.5 mumol/GHb in TR, 13.8 +/- 2.2 mumol/gHb in ST). There were remarkable differences in the shape of the curves between the groups. The slope "n" in the Hill plot amounted to 2.65 +/- 0.12 in UT, 2.74 +/- in ST and 2.90 +/- 0.11 in the TR (2 p against UT less than 0.001), leading to an elevated oxygen pressure of about 2 Torr (0.27 kPa) at 20% saturation and an augmented oxygen extraction of 5--7 SO2 at a PO2 of about 15 Torr (2kPa), which might be favorable at high workloads. The reason for the phenomenon could be an increased amount of young red cells in the blood of TR, caused by exercise induced hemolysis.  相似文献   

8.
Oxygen binding curves (OEC) for red cell suspensions have a biphasic shape and reduced n50 values when the concentration of 2,3-diphosphoglycerate (DPG) is lowered by aging or experimental procedures. The mechanism for the abnormal shape of the OEC has been related to variations in the activity of free DPG. DPG binds to tetrameric Hb at a single site, and in red cells its normal concentration is equivalent to that of tetrameric Hb. This equivalence renders the oxygen affinity of Hb and the shape of the OEC very sensitive to small changes in the activity of DPG. The OEC for stripped Hb solutions in the presence of nonsaturating concentrations of DPG also exhibit a biphasic shape but with much larger changes in the n values than observed for red cells. Upon addition of chloride, a known competitor of DPG binding to Hb, the shape of the OEC becomes similar to that of red cell suspensions with the same DPG/Hb ratio. Studies on Hb solutions in the presence of varying concentrations of DPG, but without chloride, have revealed that the cofactor shifts the entire OEC to the right, including both its upper and lower asymptotes. This finding indicates that DPG lowers the intrinsic oxygen affinity for both the T and R states. Theoretical considerations leading to a successful modeling of OEC obtained under varying conditions of DPG and chloride require an expanded two-state allosteric model in which allowance is made for DPG-dependent variations in the dissociation constants of oxygen for both the T and R conformations.  相似文献   

9.
1. A detailed account is given of an electrolytic method for determining the oxygen dissociation curve of fish blood using a single sample of 50-100 mul for the whole curve. The accuracy and some of the problems arising from its uses are discussed. 2. Oxygen dissociation curves have been determined for trout blood and human blood at temperatures of 15 and 37 degrees C. The relationship between P50 and temperature is similar to that obtained using other methods. Absolute values of P50 are generally lower than those obtained by other methods, especially in the case of fish blood. 3. The effect of PCO2 and pH on the oxygen dissociation curve of trout blood is tested and it is shown that PCO2 has a more marked effect than pH when the other factor is maintained at a constant level. The Bohr factor (delta log P50/delta pH) appears to be approximately the same and independent of the PCO2. 4.The P50 of ray blood determined from fish during and after an operation showed an increased Bohr factor.  相似文献   

10.
血红蛋白携氧-释氧动力学研究   总被引:2,自引:0,他引:2  
Jiang C  Wang X  Gao W  Peng WY  Xie JX  Li YJ 《生理学报》2008,60(1):83-89
本文研究了鸡、家兔、鲤鱼、蟾蜍4种实验动物血红蛋白(hemoglobin,Hb)携氧-释氧动力学过程,初步建立Hb携氧-释氧动力学研究方法,并探讨Hb携氧-释氧动力学过程与动物生存环境之间的关系.结果显示:4种动物Hb携氧动力学曲线均呈"S"形曲线特征,与传统的Hb氧解离曲线(oxygen dissociation curve,ODC)相似;同时不同动物Hb携氧-释氧动力学曲线也有各自特点,如鸡Hb释氧时间长达(1 411±6)S;在Hb携氧.释氧曲线I阶段,鲤鱼上升斜率远大于家兔等.提示Hb携氧-释氧动力学曲线可反映不同动物Hb携氧效率的差异.与传统ODC参数P50相对应,由动力学曲线可得到Hb携氧动力学参数T50°T50是Hb达到50%氧饱和度所需时间,可直观反映Hb携氧效率的差异.4种实验动物Hb均有较稳定的T50,从大到小依次为:鸡、家兔、鲤鱼和蟾蜍.对Hb携氧动力学曲线与ODC综合分析,可得到Hb携氧效能参数E50,表示Hb达到50%氧饱和度所用时间与环境氧分压之间的关系,即E50(50% Sat,Xeo2,yr).E50有可能成为全面评价Hb携氧效能的综合指标.  相似文献   

11.
Large amounts of intraerythrocyte 2-3 diphosphoglycerate (2-3 DPG) increase red cell oxygen-releasing capacity. Since glycosylated hemoglobins, found in higher percentages in diabetics, have an increased oxygen affinity, 2-3 DPG concentration was assayed in 12 diabetics (4 I.D.D., 8 N.I.D.D.) and 18 healthy volunteers. 2-3 DPG was related to glycemic fasting values and to glycosylated hemoglobins to evaluate if 2-3 DPG levels increase in diabetics as a compensatory mechanism to prevent peripheral hypoxia. 2-3 DPG values were significantly higher in diabetics than in normals: 11.4 mumol/gHb +/- 1.7 (= M +/- 1 SD) vs 9.8 mumol/gHb +/- 2.3 (p less than 0.05). 2-3 DPG did not correlate significantly to glycosylated hemoglobins or to glycemic values neither in diabetics nor in normals. These preliminary observations emphasize the usefullness of 2-3 DPG assay in evaluating peripheral oxygenation in diabetics: 2-3 DPG is higher in diabetics but does not correlate to glycemic equilibrium.  相似文献   

12.
Effect of hydrostatic pressure (HP) on whole blood (WB) or erythrocyte suspension hemoglobin (Hb) O2 affinity has been studied using newly developed techniques. O2 partial pressure at which hemoglobin is half-saturated with O2 (P50) measurements were made at 5 HP (1, 26, 51, 76, and 126 ATA) on thin films of human WB or erythrocytes at 37 degrees C. CO2 partial pressure of WB was either 28 or 57 Torr (film pH 7.51 or 7.31). HP increased affinity of erythrocytes and WB. For erythrocytes in tris(hydroxymethyl)aminomethane buffer, the ratio (r) of P50 (1 ATA)/P50 (51 ATA) was 1.089 (P less than 0.01) at pH 7.0. WB P50 decreased with HP at a rate of -3.3 X 10(-2) Torr X atm-1; change in P50 at higher HP vs. 1 ATA was highly significant (P less than 0.01). No effect of HP was seen on the CO2 Bohr coefficient. Inert gas choice, N2 vs. helium (He), had no effect. Measurement of decrease of P50 with HP at 76 ATA in hemolyzed WB gave an r of 1.15, as great or greater than that found in WB, indicates that Donnan equilibrium alteration is not involved. No effect of HP was found in WB on the ratio of P50 of erythrocytes with normal (5 mmol/l erythrocytes) 2,3-diphosphoglycerate (DPG) to P50 of erythrocytes with less than 5% of normal DPG; i.e., no effect of pressure was seen on the independent influence of DPG on P50. WB measurements of Hb O2 uptake under simulated physiological conditions are characterized by a net decrease in partial molal volume on oxygenation of 30-35 ml/mol Hb4.  相似文献   

13.
The linkage between the four-step binding of oxygen and the binding of heterotropic anionic ligands in hemoglobin was investigated by accurately measuring and analyzing the oxygen equilibrium curves of human adult hemoglobin in the presence and absence of various concentrations of one or two of the following materials: chloride (Cl-), 2,3-diphosphoglycerate (DPG), and inositol hexaphosphate (IHP). Each equilibrium curve was analyzed according to the Adair equation to evaluate the four-step oxygen equilibrium constants (Adair constants) and the median oxygen pressure. The binding constants of the anions for the molecular species of hemoglobin carrying j oxygen molecules, Hb(O2)j(j=0,1,...,4), were evaluated from the dependences of the Adair constants and the median oxygen pressure on the anion concentration by introducing a model which takes the competitive binding of Cl- and DPG or IHP into account. Assumptions made in the model are: (a) the hemoglobin molecule has two oxygen-linked binding sites for Cl- which are equivalent and independent and (b) no Cl- can be bound to hemoglobin to which DPG or IHP is already bound and vice versa. Thus, we could obtain values for the intrinsic binding constants of Cl- and DPG, i.e., the constants in the absence of other competitive anions. For IHP, only the binding constants and apparent binding constants for Hb and Hb(O2)2 were obtained. Values of the Cl- binding constants and apparent binding constants for DPG and IHP, i.e., the binding constants in the presence of Cl- for Hb and Hb(O2)4, were in reasonable agreement with literature values. From the binding constants we calculated anion binding curves for Hb(O2)j(J=0,1,...,4), the number of anions bound to Hb(O2)J, And the relationship between fractional anion saturation of hemoglobin and fractional oxygen saturation. The numbers of released anions are not uniform with respect to oxygenation step. This non-uniformity is the reason for the changes in the shape of the oxygen equilibrium curve with anion concentration changes and for the non-uniform dependences of the Adair constants on anion concentration, and also results in non-linear relations between anion saturation and oxygen saturation. The anion binding constants and various binding properties of the anions derived from those constants are consistent with those observed by other investigators using different techniques, indicating that the present model describes the oxygen-linked competitive anion binding well.  相似文献   

14.
Nitric oxide (NO) has high affinity to heme and by interaction with oxyhemoglobin (HbO2) is converted into nitrate to form methemoglobin (MetHb) as a side product. In combining with deoxy-Hb NO yields a stable molecule of nitrosyl-hemoglobin (HbFe(II)NO) that can further be converted into nitrate and hemoglobin (Hb). In addition, Hb was shown to transport NO in a form of S-nitrosohemoglobin (SNO-Hb). These features of the Hb and NO interaction are important for blood oxygen transport including hemoglobin-oxygen affinity (HOA). The present investigation was aimed to study the blood oxygen transport indices (pO2, pCO2, pH, HOA, etc.) in rats under hypothermia combined with a modification of L-arginine-NO pathway. To modify the L-arginine-NO pathway, rats were administered with N(G)-nitro-L-arginine methyl ester (L-NAME), L-arginine, or sodium nitroprusside (SNP) intravenously before cooling. A substantial impairment of oxygen delivery and development of hypoxia, with an important contribution of HOA into the latter accompanied the deep hypothermia in rats. All the experimental groups developed metabolic acidosis, less pronounced in rats treated with L-arginine only. In the experiments with a modification of the L-arginine-NO pathway, an enhanced cold resistance, attenuated oxygen deficiency, and a weaker oxyhemoglobin dissociation curve (ODC) shift leftwards were observed only after the administration of L-arginine. Neither SNP nor L-NAME had not any protective effects. L-Arginine lowered the value of standard P50 (pO2, corresponding to 50% Hb saturation with oxygen at 37 degrees C, pH 7.4, and pCO2 = 40 mmHg). The actual P50 (at actual pH, pCO2 and temperature) decreased by approximately 15 mmHg and was significantly higher than that under hypothermia without the drug treatment (21.03 +/- 0.35 vs 17.45 +/- 0.60 mmHg). NO also can contribute to this system through different mechanisms (HOA modification, vascular tone regulation, peroxynitrite formation, and effects).  相似文献   

15.
The O2 binding properties of bovine Hb were examined. The increase in Cl- and DPG concentration enhanced P50. A reduction in n(max) was observed at high Cl- concentration, while DPG had little effect on n(max). An increase in Cl- concentration enhanced the Bohr effect, the magnitude of which reached a maximum at 0.1 M Cl- and 20 degrees C. This concentration is nearly equal to that at the highest slope of the log P50 vs. log [Cl-] plot, and also equal to the physiological Cl- concentration (0.1 M) of bovine blood. Furthermore, the influence of Cl- concentration on the Bohr effect is independent of temperature. On the other hand, in the absence of Cl-, bovine Hb is sensitive to DPG; an increase in DPG concentration enhanced the Bohr effect, which reached a maximum at 3 mM DPG and 20 degrees C. This concentration is nearly equal to that at the highest slope of the log P50 vs. log [DPG] plot. At low DPG concentrations, the DPG effect on the Bohr effect became small with increasing temperature, whereas at high DPG concentrations, the DPG effect was insensitive to temperature changes. At the physiological concentration of DPG (0.5 mM), increases in both Cl- concentration and temperature diminished the DPG effect. At the physiological concentrations of Cl- and DPG, the Bohr effect was -0.36 at 37 degrees C. The deltaH value at the physiological concentrations of Cl- and DPG was approximately -5.8 kcal/mol at pH 7.4. These results indicate that Cl- and temperature are important determinants of the O2 binding properties of bovine Hb.  相似文献   

16.
Oxygen transport characteristics and phosphate compounds were measured in the blood of reedfish, Erpetoichthys calabaricus, a bimodal breather. Blood from reedfish possessed the following values (mean +/- SD): hematocrit (21.7 +/- 0.4%), hemoglobin concentration (7.53 +/- 1.75 g%), red blood cell count (0.45 +/- 0.10 X 10(6)/mm3) and oxygen capacity (10.1 +/- 2.3 vol%). Although hematocrit, hemoglobin concentration, red blood cell count and oxygen capacity were all highly intercorrelated (P less than 0.01 in all cases), none of these parameters were significantly correlated with sex, weight or length in our sixteen fish sample. Erythrocyte volumes equalled 480 micrometers3, showed less variation (CV = 10.4%) and did not correlate with any other measured variable. Blood oxygen dissociation curves were sigmoidal and the P50's equalled 17.34 +/- 3.04 at 1% CO2 and 25 degrees C. Mean Bohr shift (delta log P50/delta pH) was -0.274 +/- 0.087. Temperature strongly influenced blood oxygen affinity. At 1% CO2, delta log P50/delta T equalled 0.026 +/- 0.006 (mean +/- SD). These hematological properties indicate that the blood of reedfish is similar to those of other tropical air-breathering species. Concentrations of total phosphate in the erythrocytes and percentage of total phosphate bound as nucleotide triphosphates were high. Surprisingly, 2,3diphosphoglycerate was found which has been reported in the erythrocytes of only two other fish species. Blood characteristics of reedfish exposed to air for 4 hr with one exception (Hill numbers) were not significantly different from water exposed controls. This suggests that the reedfish does not possess blood respiratory mechanisms to facilitate respiration solely by air-breathing.  相似文献   

17.
  • 1.1. The entire oxygen dissociation curve (ODC) and the effects of temperature, pH and 2,3-diphosphoglycerate (DPG) on this curve, have been compared in four mammalians: man, dog, horse and cattle.
  • 2.2. If the oxyphoric capacities are similar between these species (around 1.39ml O2/gHb), their P50, measured in standard conditions, i.e. at pH 7.4;.pCO2 40mmHg and T 37°C, varies between 23.8 (± 0.8) mmHg for the horse, 25.0 (± 1.4) mmHg for cattle, 26.6 (± 1.2) for man and 28.8 (± 2.6) mmHg for the dog.
  • 3.3. The higher dispersion of the dog's P50 is due to difference between breeds; in seven breeds investigated, the P50 ranges from 25.8 (spaniel) to 35.8 (hound).
  • 4.4. We noted no sex difference in the four species.
  • 5.5. The DPG level is confirmed to be low in cattle (< 1 μmol/gHb) as compared to man (13.5 ± 2.1 gmmol/gHb), horse (16.9 ± 1.1 gmmol/gHb) and dog (19.4 ± 2.8 μmol/gHb).
  • 6.6. The oxygen exchange fraction defined as the difference in vol% between a pO2 of 80 and 35 mmHg is, respectively, 3.6 (± 0.6) vol% for cattle, 4.0 (0.4) vol% for the horse, 5.5 (± 0.5) vol% for man and 6.6 (± 1.7) vol% for the dog.
  • 7.7. The position and shape of the ODC, as well as T, DPG and pH effects, indicate that the haemoglobin of man and dog seem better adapted to O2 delivery as compared to the horse and cattle.
  相似文献   

18.
The oxygen dissociation curve (ODC) of hemoglobin (Hb) has been widely studied and mathematically described for nearly a century. Numerous mathematical models have been designed to predict with ever-increasing accuracy the behavior of oxygen transport by Hb in differing conditions of pH, carbon dioxide, temperature, Hb levels, and 2,3-diphosphoglycerate concentrations that enable their applications in various clinical situations. The modeling techniques employed in many existing models are notably borrowed from advanced and highly sophisticated mathematics that are likely to surpass the comprehensibility of many medical and bioscience students due to the high level of "mathematical maturity" required. It is, however, a worthy teaching point in physiology lectures to illustrate in simple mathematics the fundamental reason for the crucial sigmoidal configuration of the ODC such that the medical and bioscience undergraduates can readily appreciate it, which is the objective of this basic dissertation.  相似文献   

19.
Functional parameters of the whole blood oxygen loading from 66 anemic subjects, compared with those from 66 normal adult of both sexes display the following behaviour: a) Adult males and females differ for p50 values, which are higher in females because of their lower Hb level. This difference is already well known and appears to be statistically significant. b) The same difference is amplified in anemic subjects, where also pH lowering contributes to the right-shift of p50. c) The inverse relationship between p50 and DPG values differs if analysed at the actual pHs, at pH corrected at 7.4, or extrapolated from Bohr effect. In fact, the three relative plots do not parallel, and their most significant intersects drop around 0.8-0.9 value of DPG, and 26-27 torr of p50, i.e. within normal limits.  相似文献   

20.
The Bohr effect was measured in normal whole blood and in blood with low DPG concentration as a function of oxygen saturation. pH was changed by varying CO2 concentration (CO2 Bohr effect) or by addition of isotonic NaOH or HC1 at constant PCO2 (fixed acid Bohr effect). At nornal DPG concentration CO2 Bohr effect was -0.52 at 50% blood oxygen saturation, increasing in magnitude at lower saturation and decreasing in magnitude at higher saturation. In DPG depleted blood with base excess (BE) similar to 0 meq/1, there was similar dependence of CO2 Bohr effect on oxygen saturation. At BE similar to -10 meq/1, influence of saturation was comparable, but the magnitude of the Bohr effect was markedly increased at all saturations. Fixed acid Bohr effect at normal DPG concentration was -0.45 at saturations of 50-90% but decreased at lower saturations. In DPG-depleted blood fixed acid Bohr effect averaged about -0.33 with minimal variation with saturation. Influence of DPG on oxygen affinity was greater at intermediate saturations and less at saturations below 20% and above 80%. Effect of CO2, independent of pH, was many fold greater at lower oxygen saturations than at higher saturations. These results support the suggestion that the alpha chain of hemoglobin is the site of the initial oxygenation reaction. Physiologically they indicate that the relative contribution of CO2 and fixed acid, as well as the level of oxygen saturation and DPG concentration, may be important in determining PO2 of capillary blood and resulting oxygen delivery.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号