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1.
Böning D Klarholz C Himmelsbach B Hütler M Maassen N 《European journal of applied physiology》2007,100(4):457-467
Defense of extracellular pH constancy against lactic acidosis can be estimated from changes (Δ) in lactic acid ([La]), [HCO3−], pH and PCO2 in blood plasma because it is equilibrated with the interstitial fluid. These quantities were measured in earlobe blood during
and after incremental bicycle exercise in 13 untrained (UT) and 21 endurance-trained (TR) males to find out if acute and chronic
exercise influence the defense. During exercise the capacity of non-bicarbonate buffers (βnbi = −Δ[La] · ΔpH−1 − Δ[HCO3−] · ΔpH−1) available for the extracellular fluid (mainly hemoglobin, dissolved proteins and phosphates) amounted to 32 ± 2(SEM) and
20 ± 2 mmol l−1 in UT and TR, respectively (P < 0.02). During recovery βnbi decreased to 14 (UT) and 12 (TR) mmol l−1 (both P < 0.001) corresponding to values previously found at rest by in vivo CO2 titration. Bicarbonate buffering (βbi) amounted to 44–48 mmol l−1 during and after exercise. The large exercise βnbi seems to be mainly caused by an increasing concentration of all buffers due to shrinking of the extracellular volume, exchange
of small amounts of HCO3− or H+ with cells and delayed HCO3− equilibration between plasma and interstitial fluid. Increase of [HCO3−] during titration by these mechanisms augments total β and thus the calculated βnbi more than βbi because it reduces ΔpH and Δ[HCO3−] at constant Δ[La]. The smaller rise in exercise βnbi in TR than UT may be caused by an increased extracellular volume and an improved exchange of La−, HCO3− and H+ between trained muscles and blood. 相似文献
2.
Extracellular pH defense against lactic acid in normoxia and hypoxia before and after a Himalayan expedition 总被引:3,自引:0,他引:3
Böning D Maassen N Thomas A Steinacker JM 《European journal of applied physiology》2001,84(1-2):78-86
The extracellular pH defense against the lactic acidosis resulting from exercise can be estimated from the ratios −Δ[La] · ΔpH−1 (where Δ[La] is change in lactic acid concentration and ΔpH is change in pH) and Δ[HCO3
−] · ΔpH−1 (where Δ[HCO3
−] is change in bicarbonate concentration) in blood plasma. The difference between −Δ[La] · ΔpH−1 and Δ[HCO3
−] · ΔpH−1 yields the capacity of available non-bicarbonate buffers (mainly hemoglobin). In turn, Δ[HCO3
−] · ΔpH−1 can be separated into a pure bicarbonate buffering (as calculated at constant carbon dioxide tension) and a hyperventilation
effect. These quantities were measured in 12 mountaineers during incremental exercise tests before, and 7–8 days (group 1)
or 11–12 days (group 2) after their return from a Himalayan expedition (2800–7600 m altitude) under conditions of normoxia
and acute hypoxia. In normoxia −Δ[La] · ΔpH−1 amounted to [mean (SEM)] 92 (6) mmol · l−1 before altitude, of which 19 (4), 48 (1) and 25 (3) mmol · l−1 were due to hyperventilation, bicarbonate and non-bicarbonate buffering, respectively. After altitude −Δ[La] · ΔpH−1 was increased to 128 (12) mmol · l−1 (P < 0.01) in group 1 and decreased to 72 (5) mmol · l−1 in group 2 (P < 0.05), resulting mainly from apparent large changes of non-bicarbonate buffer capacity, which amounted to 49 (14) mmol · l−1 in group 1 and to 10 (2) mmol · l−1 in group 2. In acute hypoxia the apparent increase in non-bicarbonate buffers of group 1 was even larger [140 (18) mmol · l−1]. Since the hemoglobin mass was only modestly elevated after descent, other factors must play a role. It is proposed here
that the transport of La− and H+ across cell membranes is differently influenced by high-altitude acclimatization.
Accepted: 14 September 2000 相似文献
3.
Böning D Klarholz C Himmelsbach B Hütler M Maassen N 《European journal of applied physiology》2007,99(2):163-171
It has been concluded from comparisons of base excess (BE) and lactic acid (La) concentration changes in blood during exercise-induced
acidosis that more H+ than La− leave the muscle and enter interstitial fluid and blood. To examine this, we performed incremental cycle tests in 13 untrained
males and measured acid–base status and [La] in arterialized blood, plasma, and red cells until 21 min after exhaustion. The
decrease of actual BE (−ΔABE) was 2.2 ± 0.5 (SEM) mmol l−1 larger than the increase of [La]blood at exhaustion, and the difference rose to 4.8 ± 0.5 mmol l−1 during the first minutes of recovery. The decrease of standard BE (SBE), a measure of mean BE of interstitial fluid (if)
and blood, however, was smaller than the increase of [La] in the corresponding volume (Δ[La]if+blood) during exercise and only slightly larger during recovery. The discrepancy between −ΔABE and Δ[La]blood mainly results from the Donnan effect hindering the rise of [La]erythrocyte to equal values like [La]plasma. The changing Donnan effect during acidosis causes that Cl− from the interstitial fluid enter plasma and erythrocytes in exchange for HCO3−. A corresponding amount of La− remains outside the blood. SBE is not influenced by ion shifts among these compartments and therefore is a rather exact measure
of acid movements across tissue cell membranes, but changes have been compared previously to Δ[La]blood instead to Δ[La]if+blood. When performing correct comparisons and considering Cl−/HCO3− exchange between erythrocytes and extracellular fluid, neither the use of ΔABE nor of ΔSBE provides evidence for differences
in H+ and La− transport across the tissue cell membranes. 相似文献
4.
Hideyo Yoshida Chikao Shimamoto Shigenori Ito Eriko Daikoku Takashi Nakahari 《The journal of physiological sciences : JPS》2010,60(4):273-282
Ionomycin (IM, 5 μM), which exchanges 1 Ca2+ for 1 H+, changed intracellular pH (pHi) with Ca2+ entry into rat submandibular acinar cells. IM-induced changes in pHi consisted of two components: the first is an HCO3
−-dependent transient pHi decrease, and the second is an HCO3
−-independent gradual pHi increase. IM (1 μM), which activates store-operated Ca2+ channels, induced an HCO3
−-dependent and transient pHi decrease without any HCO3
−-independent pHi increase. Thus, a gradual pHi increase was induced by the Ca2+/H+ exchange. The HCO3
−-dependent and transient pHi decrease induced by IM was abolished by acetazolamide, but not by methyl isobutyl amiloride (MIA) or diisothiocyanatostilbene
disulfonate (DIDS), suggesting that the Na+/H+ exchange, the Cl−/HCO3
− exchange, or the Na+-HCO3
− cotransport induces no transient pHi decrease. Thapsigargin induced no transient pHi decrease. Thus, IM, not Ca2+ entry, reduced pHi transiently. IM reacts with Ca2+ to produce H+ in the presence of
\textCO 2 /\textHCO 3 - : [ \textH - \textIM ] - + \text Ca 2+ + \textCO 2 \rightleftarrows [ \textH-\textCa - \textIM ] + ·\textHCO 3 - + \textH + {\text{CO}}_{ 2} /{\text{HCO}}_{ 3}{^{ - }} : \, \left[ {{\text{H}} - {\text{IM}}} \right]^{ - } + {\text{ Ca}}^{ 2+ } \,+ {\text{CO}}_{ 2} \rightleftarrows \left[ {{\text{H}}-{\text{Ca}} - {\text{IM}}} \right]^{ + } \cdot {\text{HCO}}_{ 3}{^{ - } }+ {\text{H}}^{ + } . In this reaction, a monoprotonated IM reacts with Ca2+ and CO2 to produce an electroneutral IM complex and H+, and then H+ is removed from the cells via CO2 production. Thus, IM transiently decreased pHi. In conclusion, in rat submandibular acinar cells IM (5 μM) transiently reduces pHi because of its chemical characteristics, with HCO3
− dependence, and increases pHi by exchanging Ca2+ for H+, which is independent of HCO3
−. 相似文献
5.
David Bishop Johann Edge Alberto Mendez-Villanueva Claire Thomas Knut Schneiker 《Pflügers Archiv : European journal of physiology》2009,458(5):929-936
We have previously reported an acute decrease in muscle buffer capacity (βmin vitro) following high-intensity exercise. The aim of this study was to identify which muscle buffers are affected by acute exercise
and the effects of exercise type and a training intervention on these changes. Whole muscle and non-protein βmin vitro were measured in male endurance athletes (VO2max = 59.8 ± 5.8 mL kg−1 min−1), and before and after training in male, team-sport athletes (VO2max = 55.6 ± 5.5 mL kg−1 min−1). Biopsies were obtained at rest and immediately after either time-to-fatigue at 120% VO2max (endurance athletes) or repeated sprints (team-sport athletes). High-intensity exercise was associated with a significant
decrease in βmin vitro in endurance-trained males (146 ± 9 to 138 ± 7 mmol H+·kg d.w.−1·pH−1), and in male team-sport athletes both before (139 ± 9 to 131 ± 7 mmol H+·kg d.w.−1·pH−1) and after training (152 ± 11 to 142 ± 9 mmol H+·kg d.w.−1·pH−1). There were no acute changes in non-protein buffering capacity. There was a significant increase in βmin vitro following training, but this did not alter the post-exercise decrease in βmin vitro. In conclusion, high-intensity exercise decreased βmin vitro independent of exercise type or an interval-training intervention; this was largely explained by a decrease in protein buffering.
These findings have important implications when examining training-induced changes in βmin vitro. Resting and post-exercise muscle samples cannot be used interchangeably to determine βmin vitro, and researchers must ensure that post-training measurements of βmin vitro are not influenced by an acute decrease caused by the final training bout. 相似文献
6.
Benelli P Ditroilo M Forte R De Vito G Stocchi V 《European journal of applied physiology》2007,99(6):685-693
The main purpose of this study was to measure the post-competition blood lactate concentration ([La]b) in master swimmers of both sexes aged between 40 and 79 years in order to relate it to age and swimming performance. One
hundred and eight swimmers participating in the World Master Championships were assessed for [La]b and the average rate of lactate accumulation (La′; mmol l−1 s−1) was calculated. In addition, 77 of them were also tested for anthropometric measures. When the subjects were divided into
10-year age groups, males exhibited higher [La]b than women (factorial ANOVA, P < 0.01) and a steeper decline with ageing than female subjects. Overall, mean values (SD) of [La]b were 10.8 (2.8), 10.3 (2.0), 10.3 (1.9), 8.9 (3.2) mmol l−1 in women, and 14.2 (2.5), 12.4 (2.5), 11.0 (1.6), 8.2 (2.0) mmol l−1 in men for, respectively, 40–49, 50–59, 60–69, 70–79 years’ age groups. When, however, [La]b values were normalised for a “speed index”, which takes into account swimming speed as a percentage of world record, these
sex-related differences, although still present, were considerably attenuated. Furthermore, the differences in La′ between
males and females were larger in the 40–49 age group (0.34 vs 0.20 mmol l−1 s−1 for 50-m distance) than in the 70–79 age group (0.12 vs 0.14 mmol l−1 s−1 for 50-m distance). Different physiological factors, supported by the considered anthropometric measurements, are suggested
to explain the results. 相似文献
7.
Peripheral markers of central fatigue in trained and untrained during uncompensable heat stress 总被引:1,自引:0,他引:1
Wright HE Selkirk GA Rhind SG McLellan TM 《European journal of applied physiology》2012,112(3):1047-1057
The development of fatigue is more pronounced in the heat than thermoneutral environments; however, it is unclear whether
biomarkers of central fatigue are consistent with the higher core temperature (T
c) tolerated by endurance trained (TR) versus untrained (UT) during exertional heat stress (EHS). The purpose of this study
was to examine the indicators of central fatigue during EHS in TR versus UT. Twelve TR and 11 UT males (mean ± SE
[(V)\dot]\textO 2 \textpeak \dot{V}{\text{O}}_{{ 2 {\text{peak}}}} = 70 ± 2 and 50 ± 1 mL kg LBM−1 min−1, respectively) walked on a treadmill to exhaustion (EXH) in 40°C (dry) wearing protective clothing. Venous blood was obtained
at PRE and 0.5°C T
c increments from 38 to 40°C/EXH. Free tryptophan (f-TRP) decreased dramatically at 39.5°C for the TR. Branch chain amino acids
decreased with T
c and were greater for UT than TR at EXH. Tyrosine and phenylalanine remained unchanged. Serum S100β was undetectable (<5 pg mL−1). Albumin was greater for the UT from PRE to 39.0°C and at EXH. Prolactin (PRL) responded to relative thermal strain with
similar EXH values despite higher T
c tolerated for TR (39.7 ± 0.09°C) than UT (39.0 ± 0.09°C). The high EXH PRL values for both groups support its use as a biomarker
of the serotonin and dopamine interplay within the brain during the development of central fatigue. 相似文献
8.
M. Bleich R. Warth I. Thiele R. Greger 《Pflügers Archiv : European journal of physiology》1998,436(2):248-254
Isolated in vitro perfused rectal gland tubules (RGT) were preincubated with the pH-sensitive dye 2′,7′-bis(carboxyethyl)-5(6)-carboxyfluorescein
(BCECF) and pH-regulatory mechanisms were studied. A reduction of bath Cl– concentration from 269 to 6 mmol/l increased the fluorescence ratio 488/436 [corresponding to cytosolic pH (pHi)] slightly but significantly (n=10). Depolarization by Ba2+ (1 mmol/l) or a bath solution containing 30 mmol/l K+ (n=4–6) increased the fluorescence ratio (pHi). These data suggest that HCO3
– uptake and/or H+ extrusion is dependent on Cl– and/or voltage. A reduction of bath Na+ from 278 to 5 mmol/l reduced the ratio significantly (n=3). Addition of trimethylamine (Trima+, 20 mmol/l) alkalinized cytosolic pH (n=7). Similarly, addition of NH4
+ (20 mmol/l) led to an initial alkalinization and a strong acidification when NH4
+ was removed (n=59). The initial pHi-recovery rates after NH4
+ removal were quantified and the responsible H+ extrusion and/or HCO3
– import systems were examined. The recovery was almost completely abolished when the extracellular Na+ concentration was reduced to 5 mmol/l. In the presence of normal Na+, recovery was slower in the absence as compared to the presence of HCO3
– (n=5). It was inhibited by 4,4′-diisothiocyanatostilbene-2,2′-disulphonic acid (DIDS) (0.5 mmol/l, n=11) in the presence of HCO3
– and in the absence of HCO3
– by the Na+/H+-exchange blocker HOE694 (0.5 mmol/l, n=6). These data suggest that acid extrusion probably occurs by basolateral Na+-2HCO3
–/Cl– exchange in the presence of HCO3
– and by basolateral Na+/H+ exchange in the absence of HCO3
–. Luminal perfusion with a solution containing a low Cl– concentration (6 mmol/l) increased the fluorescence ratio (pHi) (n=5). The ratio (pHi) was further increased and pH recovery further delayed by basolateral addition of Trima+ (20 mmol/l, n=3). These data suggest that the HCO3
–/Cl– exchanger is present in the luminal membrane. Luminal HCO3
–/Cl– exchange and basolateral Na+-2HCO3
–/Cl– exchange may work in tandem to secrete HCO3
– and exchange it for luminal Cl–.
Received: 7 January 1998 / Received after revision and accepted: 5 March 1998 相似文献
9.
Stumpff F Martens H Bilk S Aschenbach JR Gäbel G 《Pflügers Archiv : European journal of physiology》2009,457(5):1003-1022
The absorption of short-chain fatty acids (SCFA) from the rumen requires efficient mechanisms for both apical uptake and basolateral
extrusion. Previous studies suggest that the rumen expresses a basolateral chloride conductance that might be permeable to
SCFA. In order to characterize this conductance in more detail, isolated cultured ruminal epithelial cells were studied with
the patch-clamp technique, revealing a whole-cell conductance with p(Cl−) ≈ p(NO3
−) > p(HCO3
−) > p(acetate−) > p(gluconate−). Currents could be blocked by diisothiocyanato-stilbene-2,2′-disulfonic acid (1 mmol l−1 > 100 μmol l−1), 5-nitro-2-(3-phenylpropyl-amino)benzoic acid (50 μmol l−1), niflumic acid (100 μmol l−1), and p-chloromercuribenzoate (1 mmol l−1). Single-channel conductance was 350 ± 7 pS for chloride and 142 ± 7 pS for acetate. Open probability could be fitted with
a three-state gating model. We propose a role for this channel in mediating the permeation of chloride, bicarbonate, and acetate
across the basolateral membrane of the ruminal epithelium. 相似文献
10.
The purpose of the present study was to determine whether 12 months of endurance training reduced [Ca2+]i in T helper (CD4+) lymphocytes in trained (TR) men compared to untrained (UT). Fourteen trained (Ironman triathletes) and nine untrained (sedentary) men volunteered for the study. The TR group averaged 12 km of swimming, 300 km of cycling and 60 km of running per week during the year. Resting blood samples were taken from TR (VO2peak 64 ± 2 ml kg−1 min−1) and UT (VO2peak 42 ± 2 ml kg−1 min−1) subjects every 4 weeks for 52 weeks (October 1, 1999–October 1, 2000). Leukocyte concentration was measured using a full blood count. Unstimulated CD4+ lymphocytes were separated and analysed for changes in free ([Ca2+]i) and total ([Ca2+]t) calcium using flow cytometry. There were no significant differences in leukocyte concentration between UT and TR groups. There were significant differences between TR and UT in [Ca2+]i (October B and November), and [Ca2+]t (January and March). There were also significant sequential monthly changes in both [Ca2+]i and [Ca2+]t for TR and UT groups during the study. Significant increases in [Ca2+]i and [Ca2+]t during summer (January and March) for both TR and UT groups suggest an increase in intracellular signalling during hot weather. [Ca2+]i and [Ca2+]t were significantly lower in TR lymphocytes during November and March, suggesting that endurance training during warmer months may decrease [Ca2+]i through altered intracellular signalling, possibly to maintain lymphocyte function during heat stress. 相似文献
11.
The purpose of the present study was to determine whether 12 months of moderate intensity cycling would increase the expression
of IL-2 (CD25+) receptors in T helper (CD4+) lymphocytes in men and women aged 65–75 years. Fourteen men and 10 women completed 52 weeks of moderate intensity cycling
(60% VO2peak). Subjects trained (TR) three times per week for 45 min per session. Eight age-matched untrained (UT) male and eight
UT female subjects acted as controls. Resting blood samples were taken from TR and UT subjects every 4 weeks. Leukocyte concentration
was measured using a full blood count. PHA-stimulated CD4+ lymphocytes were analysed for changes in the expression of CD25+, by flow cytometry. Training significantly increased VO2peak (l min−1, ml kg−1 min−1) in male (+14.3, +16%) and female (+16.7, +27.8%) groups. The TR male group showed a significantly lower percentage of CD4+CD25+ than the male UT in January but the TR male percentage was significantly higher than the UT male group during February, March,
April, May, June, September B and December. The female TR group showed a significantly higher percentage CD4+CD25+ than the female UT only during July. There were also significant sequential monthly changes in the percentage of CD4+CD25+ for male and female UT and TR groups. Significant increases in the percentage of CD4+CD25+ in the male TR group suggest training-enhanced lymphocyte mitogenic responsiveness. Moderate intensity long-term training
may increase the recruitment of active memory CD4+CD25+ in men rather than women. 相似文献
12.
In vivo 4-androstene-3,17-dione and 4-androstene-3β,17β-diol supplementation in young men 总被引:1,自引:0,他引:1
Earnest CP Olson MA Broeder CE Breuel KF Beckham SG 《European journal of applied physiology》2000,81(3):229-232
To determine if known androgenic hormone precursors for testosterone in the androgen pathway would be readily transformed
to testosterone, eight male subjects [mean age 23.8 (SEM 3) years, bodymass 83.1 (SEM 8.7) kg, height 175.6 (SEM 8.5) cm]
underwent a randomized, double-blind, cross-over, placebo-controlled oral treatment with 200 mg of 4-androstene-3,17-dione (Δ4),
4-androstene-3β,17β-diol (Δ4Diol), and placebo (PL). The periods of study were separated by 7 days of washout. Blood was drawn
at baseline and subsequently every 30 min for 90 min after treatment. Analysis revealed mean area-under-the-curve (AUC) serum
Δ4 concentrations to be higher during Δ4 treatment [2177 (SEM 100) nmol · l−1] than Δ4Diol [900 (SEM 96) nmol · l−1] or PL [484 (SEM 82) nmol · l−1; P < 0.0001]. The Δ4 treatment also revealed a significant effect on total testosterone with a mean AUC [1632.5 (SEM 121) nmol · l−1] that was greater than PL [1418.5 (SEM 131) nmol · l−1; P < 0.05] but not significantly different from those observed after Δ4Diol treatment [1602.9 (SEM 119) nmol · l−1; P = 0.77]. Free testosterone concentrations followed a similar pattern where mean AUC for the Δ4 treatment [6114.0 (SEM 600) pmol · l−1] was greater than after PL [4974.6 (SEM 565) pmol · l−1; P < 0.06] but not significantly different from those observed after Δ4Diol [5632.0 (SEM 389) pmol · l−1; P = 0.48]. The appearance and apparent conversion to total and free testosterone over 90 min was stronger for the Δ4 treatment (r = 0.91, P < 0.045) than for Δ4Diol treatment (r = 0.69, NS) and negatively correlated for PL (r = −0.90, P < 0.02). These results would suggest that Δ4, and perhaps Δ4Diol, taken by month are capable of producing in vivo increases
in testosterone concentrations in apparently healthy young men as has already been observed in women after treatment with
Δ4.
Accepted: 26 August 1999 相似文献
13.
Jacob C Zouhal H Prioux J Gratas-Delamarche A Bentué-Ferrer D Delamarche P 《European journal of applied physiology》2004,91(1):35-40
In this study we investigated whether plasma catecholamine responses to the Wingate test are affected by the intensity of training in endurance-trained subjects. To do this we compared plasma adrenaline (A) and noradrenaline (NA) concentrations in response to a Wingate test in three different groups: specialist middle-distance runners (MDR) in 800-m and 1,500-m races, specialist long-distance runners (LDR) 5,000-m and 10,000-m races, and untrained subjects (UT). The maximal power (W
max) and the mean power (W) were determined from the Wingate test. Blood lactate (La), plasma A and NA concentrations were analysed at rest (La0, A0 and NA0), immediately at the end of the exercise (Amax and NAmax) and after 5 min recovery (Lamax, A5 and NA5). The ratio Amax/NAmax was considered as an index of the adrenal medulla responsiveness to the sympathetic nervous activity. At the end of the test, W
max and W were similar in the three groups but Lamax was significantly greater in MDR compared to LDR and UT [15.2 (2.2) mmol l–1, 11.7 (3.1) mmol l–1, 11.6 (1.6) mmol l–1, respectively, for MDR, LDR and UT; mean (SD)]. Concerning the plasma catecholamine concentrations in response to exercise, MDR and LDR Amax values [3.73 (1.53) nmol l–1, 3.47 (0.74) nmol l–1, respectively, for MDR and LDR] were significantly greater than those of UT [1.48 (0.32) nmol l–1] who also exhibited the lowest NAmax values [11.09 (6.58) nmol l–1] compared to MDR and LDR [20.43 (3.51) nmol l–1; 15.85 (4.88) nmol l–1, respectively, for MDR and LDR]. However, no significant differences were observed between the two trained groups either for Amax or NAmax. These results suggest that long-term endurance training can enhance plasma catecholamine concentrations in response to supramaximal exercise. However, as there were no significant differences between MDR and LDR Amax and NAmax values, the effect of the intensity of training remains to be clarified. 相似文献
14.
Gen Kuramochi Ulrich Kersting Stefan Silbernagl William H. Dantzler 《Pflügers Archiv : European journal of physiology》1996,432(6):1062-1068
This study was designed to elucidate the acid-base balance local to the collecting duct urine (CD) and vasa recta blood (VR)
in the rat renal papilla in diuresis. The pH changes were measured in both a furosemide-induced and a volume-load-induced
diuresis, whereas the PCO2 (i.e., CO2 tension) and HCO3
− concentration were measured only in a furosemide-induced diuresis. In an antidiuresis, the pH of the VR was more acidic than
that of the systemic arterial blood (ΔpH = 0.44–0.73). Additionally, the pH of the ascending VR was significantly lower than
that of the descending VR (ΔpH = 0.14–0.16). In diuresis, the pH of the CD decreased (ΔpH = 0.81–0.97), while the pH of the
descending and the ascending VR increased; however, the increase was only significant in the ascending VR (ΔpH = 0.23–0.30).
Consequently, the significant difference in the pH gradient between the descending and the ascending VR was eliminated. The
PCO2 values in the CD and the ascending VR were not different from those in antidiuresis, while the HCO3
− concentration in the CD and the ascending VR, respectively, decreased and increased significantly. Thus, in diuresis, the
decrease in the pH of the CD and the increase in the pH of the ascending VR result, respectively, from the decrease and the
increase in the HCO3
− concentration, with no changes in the PCO2 values.
Received: 5 February 1996/Received after revision and accepted: 20 May 1996 相似文献
15.
Zinner C Wahl P Achtzehn S Sperlich B Mester J 《European journal of applied physiology》2011,111(8):1641-1648
Lactate (La) and H+-ions are unequally distributed in the blood between plasma and red blood cells (RBCs). To our knowledge there is no data
concerning the effects of an oral ingestion of bicarbonate (HCO3
−) on repeated high intensity sprint exercise and La and H+ distribution between plasma and RBCs. Since an oral ingestion of HCO3
− leads to a higher efflux of La from the working skeletal muscle to the plasma, as it was shown by previous studies, this
would lead to a higher gradient of La between plasma and RBCs. Although a higher gradient leads to a higher uptake, it is
even more difficult for the RBCs to take up La fast enough, due to the more stressed transport system. Since RBCs function
to transport La from the working muscle and help to maintain a concentration difference between plasma and muscle, this potentially
increases performance during repeated sprint exercise (e.g. 4 × 30 s). The major goal of the present investigation was to
test this hypothesis. 11 male participants ingested either a solution of sodium bicarbonate (NaHCO3) or placebo (CaCO3). Thereafter all performed four maximal 30 s sprints with 5 min of passive rest. During the resting periods concentrations
of HCO3
−, La and H+ where measured in both blood compartments (plasma and RBCs). There were no significant differences in the La-ratios between
plasma and RBCs between both interventions. These results indicate that the La/H+ co-transport is not affected by an oral ingestion on NaHCO3. 相似文献
16.
Xavier Woorons Nicolas Bourdillon Henri Vandewalle Christine Lamberto Pascal Mollard Jean-Paul Richalet Aurélien Pichon 《European journal of applied physiology》2010,110(2):367-377
Eight men performed three series of 5-min exercise on a cycle ergometer at 65% of normoxic maximal O2 consumption in four conditions: (1) voluntary hypoventilation (VH) in normoxia (VH0.21), (2) VH in hyperoxia (inducing hypercapnia) (inspired oxygen fraction [FIO2] = 0.29; VH0.29), (3) normal breathing (NB) in hypoxia (FIO2 = 0.157; NB0.157), (4) NB in normoxia (NB0.21). Using near-infrared spectroscopy, changes in concentration of oxy-(Δ[O2Hb]) and deoxyhemoglobin (Δ[HHb]) were measured in the vastus lateralis muscle. Δ[O2Hb − HHb] and Δ[O2Hb + HHb] were calculated and used as oxygenation index and change in regional blood volume, respectively. Earlobe blood samples
were taken throughout the exercise. Both VH0.21 and NB0.157 induced a severe and similar hypoxemia (arterial oxygen saturation [SaO2] < 88%) whereas SaO2 remained above 94% and was not different between VH0.29 and NB0.21. Arterialized O2 and CO2 pressures as well as P50 were higher and pH lower in VH0.21 than in NB0.157, and in VH0.29 than in NB0.21. Δ[O2Hb] and Δ[O2Hb − HHb] were lower and Δ[HHb] higher at the end of each series in both VH0.21 and NB0.157 than in NB0.21 and VH0.29. There was no difference in Δ[O2Hb + HHb] between testing conditions. [La] in VH0.21 was greater than both in NB0.21 and VH0.29 but not different from NB0.157. This study demonstrated that exercise with VH induced a lower tissue oxygenation and a higher [La] than exercise with NB.
This was caused by a severe arterial O2 desaturation induced by both hypoxic and hypercapnic effects. 相似文献
17.
Tina B. Jensen Ulla G. Friis Torben Johansen 《Pflügers Archiv : European journal of physiology》1998,436(3):357-364
The purpose of this study was to examine how intracellular pH (pHi) regulation and histamine release are affected by HCO3
–in rat peritoneal mast cells. The pHi was measured using the pH-sensitive dye 2′, 7′-bis(2-carboxyethyl)-5(6)-carboxyfluorescein (BCECF). We observed a pHi of 6.88±0.012 (n=24) in resting mast cells exposed to a HEPES buffer (pH 7.4), but a sustained drop of 0.21 pH units to 6.67±0.015 (n=23) when we exposed the mast cells to a HEPES/HCO3
–buffer equilibrated at all time with 5% CO2 (pH 7.4). This fall in pHi is inhibited by the carbonic anhydrase inhibitor dichlorphenamide and is Na+-independent, indicating the involvement of Na+-independent Cl–/HCO3
–exchange activity. Furthermore removal of external Cl–in the presence but not in the absence of HCO3
–reversed the Cl–/HCO3
–exchange and induced an alkaline load. The recovery from this alkaline load was dependent on external Cl–but independent of Na+. Both the alkalinization and the recovery were inhibited by the anion transport inhibitor 4,4′-diisothiocyanatostilbene-2,2′-disulphonic
acid (DIDS). In addition, 36Cl–uptake measurements confirm the presence of a Cl–/HCO3
–exchanger. Histamine release stimulated by antigen and compound 48/80 was substantially reduced in the presence of HEPES/
HCO3
–buffer (pHo 7.4, pHi 6.66). Histamine release was increased, however, when pHi was clamped to 6.66 in HCO3
–-free media (pHo 6.9). We conclude that: (1) Na+-independent Cl–/HCO3
–exchange determines steady-state pHi in rat peritoneal mast cells; and (2) the reduction in histamine release observed in the presence of HCO3
–is not due to its effect on pHi per se, but rather on other changes in ion transport.
Received: 29 January 1998 / Received after revision and accepted: 3 April 1998 相似文献
18.
Hütler M Woweries S Leithäuser R Böning D Beneke R 《European journal of applied physiology》2001,85(1-2):151-156
Levels of α-tocopherol (αT) in plasma and red blood cells (RBC) are assumed to be modulated by exercise. The mechanisms involved
remain to be established. We examined the influence of different running bouts on the content of αT in RBC (αTRBC), the concentration in plasma (αTplasma), and their relationship with lipolysis, as indicated by changes (Δ) in plasma glycerol concentration ([glycerol]). Eleven
healthy runners [mean (SD) age 35 (9) years, height 177.3 (7.6) cm, body mass 69.6 (9.4) kg, and peak oxygen consumption,
, 57.8 (4.8) ml.kg–1.min–1] performed an incremental treadmill test [duration 17 (2) min, peak velocity, v
peak 4.8 (0.4) m.s–1], a training run [173 (12) min, 57 (4)% v
peak] and a marathon [197 (24) min, 75 (5)% v
peak]. Before (pre) and after (post) each run, haematological and lipid parameters, αTRBC and αTPlasma were determined. Haemoconcentration was observed after each run. Δ[glycerol] was +0.10 (0.10) mmol.l–1, +0.40 (0.14) mmol.l–1 and +0.51 (0.15) mmol.l–1 in the treadmill test, training run and marathon, respectively. When corrected for haemoconcentration, values of αTplasma decreased [–5.4 (7.5)%, P<0.05] in the treadmill test, were unchanged [+0.7 (8.7)%] in the training run and increased [+7.8 (8.3)%, P<0.05] in the marathon. αTRBC decreased [pre vs post: 22.7 (3.2) nmol.g haemoglobin–1 (nmol.g Hb–1) vs 18.9 (3.8) nmol.g Hb–1, P<0.05] in the treadmill test and was not significantly changed in either the training run [20.8 (1.9) nmol.g Hb–1 vs 19.1 (3.0) nmol.g Hb–1] or the marathon [21.6 (2.9) nmol.g Hb–1 vs 23.4 (2.7) nmol.g Hb–1]. ΔαTRBC and ΔαTplasma were positively related to Δ[glycerol]. The reduction in αTRBC and αTplasma after short-lasting heavy exercise indicates the consumption of αT, whereas the association between ΔαT and Δ[glycerol] suggests
mobilisation of αT, especially in long-lasting exercises. However, although αT appears to be influenced by exercise, the results
suggest a well-balanced regulation of αT during exercise resulting in small, and only in part, significant ΔαT in blood.
Electronic Publication 相似文献
19.
Tsintzas K Simpson EJ Seevaratnam N Jones S 《European journal of applied physiology》2003,89(2):217-220
The aim of this study was to compare whole-body glucose uptake in cycling and running performed during physiological hyperinsulinaemia.
On three occasions, seven male subjects underwent a hyperinsulinaemic (30 mU m−2 min−1), euglycaemic (5 mmol l−1) clamp for 120 min. On one occasion, subjects rested for the duration of the trial (CON). On the other two occasions, after
an initial resting period of 30 min, subjects either cycled (CYC) or ran (RUN) for 90 min at 65% of maximal O2 uptake (V˙O2max). Insulin infusion resulted in physiological hyperinsulinaemia that was maintained for the duration of each trial [CON: 61
(3) mU l−1; CYC: 77 (7) mU l−1; RUN: 77 (5) mU l−1]. The rate of glucose uptake was greater during RUN than during CYC [last 30 min of exercise: 140 (4) vs 109 (8) μmol kg−1 min−1, respectively; P <0.01]. A differential amount of active muscle mass and/or muscle fibre type recruitment might account for the observed differences
in glucose disposal between cycling and running.
Electronic Publication 相似文献
20.
Dorel S Bourdin M Van Praagh E Lacour JR Hautier CA 《European journal of applied physiology》2003,89(2):157-165
The purpose of this study was to investigate the effect of two cycling velocities on power output and concomitant metabolic
and cardiorespiratory responses to repeated all-out exercises. Mean power output (P
m), total work (W
tot), total oxygen consumption (VO2tot) and blood lactate accumulation (Δ[La]b) were evaluated in 13 male subjects who performed two series of twelve 5-s bouts of sprint cycling. Recovery periods of 45-s
were allowed between trials. One series was executed at optimal velocity (V
opt: velocity for greatest power) and the other one at 50% V
opt (0.5V
opt). Velocities obtained in these conditions were Vopt=116.6 (4.7) rpm; 0.5Vopt=60.6 (4.9) rpm. After a phase of adaptation in oxygen uptake in the first part of the series, the data from the 6th to the
12th sprint were as follows: P
m, 924.6 (73.9) versus 689.2 (61.8) W; W
tot, 29.95 (4.14) versus 22.04 (3.17) kJ; VO2tot, 12.80 (1.36) versus 10.58 (1.37) l; Δ[La]b, 2.72 (1.22) versus 0.64 (0.79) mmol.l−1, respectively (P<0.001). Both W
tot and VO2tot were consistently higher at optimal velocity (+21 and +35.8%, respectively). The present findings demonstrate that during
intermittent short-term all-out exercise requiring maximal activation, the energy turnover is not necessarily maximal. It
depends on muscle contraction velocity. The increase, lower than expected, in metabolic response from 0.5V
opt to V
opt suggests also that mechanical efficiency is higher at V
opt.
Electronic Publication 相似文献