scholarly journals Hypoxic Responses in a Fish From a Stable Environment: Blood Oxygen Transport in the Antarctic Fish Pagothenia Borchgrevinki

1989 ◽  
Vol 141 (1) ◽  
pp. 97-111 ◽  
Author(s):  
R. M.G. WELLS ◽  
G. C. GRIGG ◽  
L. A. BEARD ◽  
G. SUMMERS
Keyword(s):  
Haemoglobin Concentration ◽  
Oxygen Affinity ◽  
Antarctic Fish ◽  
Hypoxic Exposure ◽  
Blood Oxygen ◽  
Low Oxygen ◽  
Pagothenia Borchgrevinki ◽  
Oxygen Carrying Capacity ◽  
O2 Delivery ◽  
The Antarctic

The effects of hypoxic exposure on whole-blood oxygen-affinity were examined in the antarctic fish Pagothenia borchgrevinki. Fish exposed to POO2 = 60 mmHg for 11–14 days at −1.5°C had a P50 value of 20.6±4.8mmHg (S.D., N=13) at pH8.16, compared with 31.1 ±4.3mmHg (N=10) at pH8.00 for normoxic fish. Exposure to low oxygen levels resulted in a significant (66 %) rise in haemoglobin concentration, and erythrocyte [ATP] decreased by approximately 27%. There was no evidence for erythrocyte swelling. An aberrant gill morphology was observed in six fish and these showed unexpectedly high erythrocyte ATP levels. Oxygen-carrying capacity increased by approximately 40% in hypoxic fish and was correlated with a 34 % decrease in spleen mass. Despite the fact that antarctic fish have exceptionally low demands for oxygen and are unlikely ever to encounterenvironmental hypoxia, this antarctic fish has the necessary machinery to respondto hypoxia in a way that is typical of teleosts that naturally inhabit oxylabile environments. The ability to make short-term adaptive changes in the O2 delivery system in response to hypoxic exposure may be typical for vertebrates in general, rather than a feature seen only in those organisms which encounter environmental hypoxia on a regular basis.

scholarly journals Antarctic Fish Blood: Respiratory Properties and the Effects Of Thermal Acclimation

1984 ◽  
Vol 109 (1) ◽  
pp. 265-279
Author(s):  
VILHELM TETENS ◽  
RUFUS M. G. WELLS ◽  
ARTHUR L. DEVRIES
Keyword(s):  
Oxygen Affinity ◽  
Antarctic Fish ◽  
Thermal Acclimation ◽  
Temperate Species ◽  
Molar Ratio ◽  
Oxygen Binding ◽  
Blood Oxygen ◽  
Low Oxygen ◽  
Blood Oxygen Affinity

1. The effects of thermal acclimation on whole blood oxygen affinity were examined in the antarctic fish Pagothenia borchgrevinki. 2. 4.5°C-acclimated fish had a P50 value of 26.7 mmHg at pH 8.1, compared to 20.7 mmHg for −1.5°C-acclimated fish. The apparent heat of oxygenation, ΔH = −26.7 kJ mol−1, is comparable to values for temperate species. 3. Warm-acclimation was followed by an increased ATP: Hb4 molar ratio, resulting in an augmentation of the thermal effect on oxy-haemoglobin affinity. This may be considered adaptive in a constantly well oxygenated environment, where oxygen loading at the gills is secured. Unloading to the tissues is thereby enhanced, supporting an elevated rate of aerobic metabolism at higher temperatures. 4. In vivo blood pH was high, between 8.10 and 8.25 at −1.5°C. Astrup titration revealed arterial CO2 tensions of less than 0.8 mmHg, indicating relative hyperventilation and low oxygen extraction efficiency in antarctic fish. 5. Blood oxygen affinities of four antarctic nototheniid species were low (P50 between 11.9 and 20.7 mmHg at pH 8.1 and --1.5°C) in comparison with the temperate species Notothenia angustata (P50 = 10.8 mmHg). The zoarcid Rhigophila dearborni had a high blood oxygen affinity (P50 = 4.3 mmHg). Blood oxygen-binding properties are discussed in relation to the polar environment, mode of life, and the concept of cold adaptation.

scholarly journals Decline of erythropoietin formation at continuous hypoxia is not due to feedback inhibition

1990 ◽  
Vol 258 (5) ◽  
pp. F1432-F1437 ◽  
Author(s):  
K. U. Eckardt ◽  
J. Dittmer ◽  
R. Neumann ◽  
C. Bauer ◽  
A. Kurtz
Keyword(s):  
Feedback Inhibition ◽  
Hypoxic Exposure ◽  
Blood Oxygen ◽  
Hormone Production ◽  
Early Increase ◽  
Mrna Content ◽  
Consistent Change ◽  
Oxygen Carrying Capacity ◽  
Kinetics Of ◽  
Serum Erythropoietin

Serum erythropoietin (EPO) levels in response to hypoxia are known to decline before an increase in blood oxygen carrying capacity. To define the possible mechanisms underlying this phenomenon, we have investigated 1) how renal EPO mRNA content and EPO production rate underlying the early kinetics of serum EPO levels change under different degrees of normobaric hypoxia, and 2) if a feedback inhibition of either EPO formation or EPO survival in the circulation exists by the hormone itself. We found that serum immunoreactive EPO levels in rats peaked after 12-h exposure to 7.5 or 9% oxygen (2,949 +/- 600 and 756 +/- 108 mU/ml, respectively, mean +/- SE) and declined to 29 and 64% of peak levels, respectively, after 36 h of hypoxia. EPO levels in response to 11.5% oxygen showed no consistent change between 12 (122 +/- 21 mU/ml, mean +/- SE) and 36 h (182 +/- 35 mU/ml) of hypoxia. The decline in EPO levels under severe hypoxia (7.5% O2) was paralleled by a marked reduction in renal EPO mRNA content, indicating that it was primarily a result of diminished hormone production. The observed reductions in serum EPO after 36 h corresponded to preceding declines of calculated EPO production rates from 163- to 62-fold (7.5% O2) and 36- to 25-fold (9% O2) basal values. Application of 50 IU recombinant human EPO to rats 12 h, 6 h, or immediately before hypoxic exposure to mimic the early increase in EPO levels did not affect endogenous EPO formation during a subsequent hypoxic exposure of 12 h.(ABSTRACT TRUNCATED AT 250 WORDS)

Chronic hypoxia and the cerebral circulation

2006 ◽  
Vol 100 (2) ◽  
pp. 725-730 ◽  
Author(s):  
Kui Xu ◽  
Joseph C. LaManna
Keyword(s):  
Blood Flow ◽  
Carrying Capacity ◽  
Hemoglobin Concentration ◽  
Capillary Density ◽  
Hypoxic Exposure ◽  
Blood Oxygen ◽  
Brain Capillary ◽  
Blood Flow Increase ◽  
Time Courses ◽  
Oxygen Carrying Capacity

Exposure to mild hypoxia elicits a characteristic cerebrovascular response in mammals, including humans. Initially, cerebral blood flow (CBF) increases as much as twofold. The blood flow increase is blunted somewhat by a decreasing arterial Pco2 as a result of the hypoxia-induced hyperventilatory response. After a few days, CBF begins to fall back toward baseline levels as the blood oxygen-carrying capacity is increasing due to increasing hemoglobin concentration and packed red cell volume as a result of erythropoietin upregulation. By the end of 2 wk of hypoxic exposure, brain capillary density has increased with resultant decreased intercapillary distances. The relative time courses of these changes suggest that they are adjusted by different control signals and mechanisms. The CBF response appears linked to the blood oxygen-carrying capacity, whereas the hypoxia-induced brain angiogenesis appears to be in response to tissue hypoxia.

Regulation of Blood Oxygen Affinity in the Australian Blackfish Gadopsis Marmoratus: I. Correlations between Oxygen-binding Properties, Habitat and Swimming Behaviour

1982 ◽  
Vol 99 (1) ◽  
pp. 223-243
Author(s):  
G. P. DOBSON ◽  
J. BALDWIN
Keyword(s):  
Whole Blood ◽  
Oxygen Affinity ◽  
Swimming Behaviour ◽  
Oxygen Binding ◽  
Blood Oxygen ◽  
Low Oxygen ◽  
Binding Properties ◽  
Molar Ratios ◽  
Blood Oxygen Affinity ◽  
Low Oxygen Affinity

1. The regulation of whole blood oxygen affinity in the freshwater blackfish Gadopsis marmoratus Richardson has been examined, and correlations made between oxygen-binding properties and the habitat and swimming behaviour of the fish. 2. Blackfish whole blood has a low oxygen affinity relative to other fish bloods reported in the literature. This is not due to a low oxygen affinity of the stripped haemoglobins, but arises from interactions between haemoglobin and intraerythrocytic modulators. 3. The presence of high concentrations of ATP, and to a lesser extent GTP, in the erythrocyte, together with the effect of these nucleoside triphosphates on the oxygen affinity of haemoglobin solutions at physiological NTP: Hb4 molar ratios, demonstrates that this class of compounds is a major regulator of oxygen affinity in blackfish blood. 4. The oxygen affinities of whole blood and haemoglobin solutions are sensitive to pH, with haemoglobin solutions displaying a relatively large alkaline Bohr coefficient of - 1.05 over the physiologically relevant pH range of 6.5–7.0. 5. Although increasing Pco2, lowers the oxygen affinity of whole blood, it does so only through the effect on pH, as pH-buffered haemoglobin solutions show no oxygen-linked CO2 binding. This lack of oxygen-linked CO2 binding has not been reported for any other naturally occurring vertebrate haemoglobins. 6. Muscle morphology and biochemistry, and behavioural observations, indicate that the blackfish uses anaerobic energy metabolism during rapid swimming and in recovery. 7. It is concluded that the oxygen-binding properties of blackfish blood reflect adaptations for maintaining adequate tissue oxygenation for animals at rest and during slow sustained swimming in waters of high oxygen tensions.

A role of 5-HT2 receptors in the gill vasculature of the antarctic fish Pagothenia borchgrevinki.

1998 ◽  
Vol 201 (14) ◽  
pp. 2129-2138 ◽  
Author(s):  
L Sundin ◽  
W Davison ◽  
M Forster ◽  
M Axelsson
Keyword(s):  
Receptor Antagonist ◽  
Vascular Resistance ◽  
Receptor Agonist ◽  
Antarctic Fish ◽  
Cardiovascular Responses ◽  
Arterial Oxygen ◽  
Nerve Fibres ◽  
Aortic Blood ◽  
Pagothenia Borchgrevinki ◽  
The Antarctic

This study was conducted to describe the cardiovascular responses to intra-arterial injections of serotonin in the Antarctic fish Pagothenia borchgrevinki and to elucidate the underlying mechanisms. Immunohistochemistry was used to localise serotonin-containing cells within the gills. Simultaneous and continuous recordings of ventral and dorsal aortic blood pressure, heart rate and ventral aortic blood flow (cardiac output) were made using standard cannulation procedures in combination with Doppler flow measurement. An extracorporeal loop with an in-line oxygen electrode allowed continuous measurements of arterial oxygen pressure PaO2. Pre-branchial injection of serotonin (5-hydroxytryptamine, 5-HT) or the 5-HT2 receptor agonist alpha-methylserotonin increased the branchial vascular resistance and ventral aortic pressure, while the 5-HT1 receptor agonist piperazine was without effect. The branchial vasoconstriction produced by serotonin injection was completely blocked by the 5-HT1/5-HT2 receptor antagonist methysergide and the branchial vasoconstriction produced by WIDTH="9" HEIGHT="12" ALIGN="BOTTOM" NATURALSIZEFLAG= alpha-methylserotonin injection was completely blocked by the specific 5-HT2 receptor antagonist LY53857. The results suggest that the 5-HT2 receptor alone mediates the branchial vasoconstriction. Serotonin also mediated a methysergide-sensitive reduction in PaO2, the reduction being greatest when the pre-injection PaO2 value was high. 5-HT-immunoreactive cells and nerve fibres were present within the gill tissues. All the 5-HT-immunoreactive cells were located on the efferent side of the filaments, but 5-HT-immunoreactive nerve fibres were found lining both of the branchial arteries. Our findings demonstrate a potential serotonergic control system for the gills in Pagothenia borchgrevinki. In contrast to its effects on the branchial vasculature, serotonin produced a methysergide-insensitive decrease in the systemic vascular resistance. However, neither the specific 5-HT1 nor 5-HT2 receptor agonists produced a decrease in the resistance of the systemic vasculature. The nature of the serotonergic receptor(s) inducing vasodilation in teleost fish is uncertain.

Nervous control of the spleen in the red-blooded Antarctic fish, Pagothenia borchgrevinki

1996 ◽  
Vol 270 (3) ◽  
pp. R599-R604 ◽  
Author(s):  
S. Nilsson ◽  
M. E. Forster ◽  
W. Davison ◽  
M. Axelsson
Keyword(s):  
Antarctic Fish ◽  
Cholinergic Innervation ◽  
Maximal Contraction ◽  
Nervous Control ◽  
Major Function ◽  
Pagothenia Borchgrevinki ◽  
The Antarctic ◽  
Stimulation Of

The mechanisms of splenic control in the Antarctic fish, Pagothenia borchgrevinki, were investigated using isolated spleen and mesenteric artery strips in vitro and perfused spleen preparations in situ. Splenosomatic index (SSI) [100 x (spleen wt/body wt)] and hematocrit were determined in animals treated with atropine and phentolamine. Atropine injection increased the SSI from 0.60 +/- 0.06 to 0.89 +/- 0.04, whereas phentolamine decreased SSI to 0.45 +/- 0.03. In atropine-injected fish, hematocrit was 18.6 +/- 1.4 before and 6.6 +/- 0.8% 3 h after injection. Electrical stimulation of the splenic nerves produced biphasic flow responses. In 11 of 12 tested preparations, atropine (3 x 10(-7) to 10(-6) M) abolished the response, suggesting a major cholinergic component in the splenic innervation. Isolated spleen strip preparations contracted in response to carbachol, a response that was antagonized by atropine. The response to acetylcholine was markedly enhanced by the specific cholinesterase inhibitor BW-284c51. Catecholamine effects were somewhat irregular, and maximal contraction force with epinephrine and norepinephrine was 41 and 56%, respectively, of the carbachol response. The results suggest a mainly, if not solely, cholinergic autonomic control of the borch spleen, and a major function of the cholinergic innervation in the control of hematocrit in this species.

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