QUICK SEARCH:   [advanced] Author: Keyword(s):
Home     Help     Feedback     Subscriptions     Archive     Search     Table of Contents

This Article Summary Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Egginton, S. Articles by Johnston, I. A. Search for Related Content PubMed PubMed Citation Articles by Egginton, S. Articles by Johnston, I. A.

Peripheral oxygen transport in skeletal muscle of Antarctic and sub-Antarctic notothenioid fish

S. Egginton^1,*, C. Skilbeck¹, L. Hoofd², J. Calvo³ and I. A. Johnston⁴

¹ Department of Physiology, University of Birmingham, Birmingham B15 2TT, UK,
² Department of Physiology, University of Nijmegen, 6525 Nijmegen, The Netherlands,
³ CONICET, CADIC, Ushuaia, Argentina and
⁴ School of Biology, Gatty Marine Laboratory, University of St Andrews, Fife KY16 8LB, Scotland

View larger version (58K): [in a new window]   Fig. 1. (A–D). Wire frame plots of calculated intracellular PO2 (kPa) in slow oxidative fibres of the locomotory (pectoral) muscles from Antarctic notothenioid species. PO2 is on the vertical axis and fibre radius (µm) on the horizontal axes, with the centre at (0,0). The highest PO2 value (6 kPa) represents that of capillaries around a fibre; this declines both radially and circumferentially, initially with a steep gradient that quickly levels out towards the inner part of the fibre. The integrated response of differences in fibre size and intracellular compartments is predicted to maintain a similar level of tissue oxygenation at a cell temperature of 0°C when fibre radius is small. When fibre girth is increased, the decrease in mean PO2 is pronounced, an effect that is accentuated within the fibres of the channichthyid Chaenocephalus aceratus, where anoxic regions are predicted to occur. See text for details.

View larger version (43K): [in a new window]   Fig. 2. Intracellular PO2 (kPa) in slow pectoral muscle fibres of notothenioids from the sub-Antarctic region. The integrated response of differences in fibre radius and intracellular compartments is predicted to maintain a similar level of tissue oxygenation at cell temperatures experienced during winter (A–D) and summer (E–H) (4 and 10°C, respectively). The icefish Champsocephalus esox shows a potential hypoxaemia that is particularly evident at the higher temperature (H).

View larger version (26K): [in a new window]   Fig. 3. Calculated intracellular PO2 (kPa) in slow pectoral muscle fibres of Mediterranean perciform fishes. The integrated response of differences in fibre radius and intracellular compartments is predicted to maintain an unvarying high level of tissue oxygenation at a cell temperature of 20°C.

View larger version (11K): [in a new window]   Fig. 4. (A) Influence of Krogh’s diffusion coefficient on the calculated mean (squares) and minimum (circles) fibre PO2. Arrowheads point to the values derived for nototheniid (left) and channichthyid (right) muscle protein concentrations. (B) Influence of capillary radius on intracellular oxygen tension. Right arrowhead, icefish vessels; left arrowhead, nototheniid vessels. (C) Influence of fibre radius on oxygenation. Right arrowhead, icefish fibres; left arrowhead, nototheniid fibres.

View larger version (19K): [in a new window]   Fig. 5. (A) The relationship between calculated mean fibre PO2 and fibre cross-sectional area (µm2) for notothenioids living at 0–20°C; the overall regression (not plotted) is PO2=6.31–0.002(fibre area) (r2=0.97). (B) The relationship between calculated mean fibre PO2 and total mitochondrial volume per unit length of fibre, V(mit,f), is V(mit,f)=Vv(mit,f)(fibre area), where V(mit,f) is mitochondrial volume density, for notothenioids living at 0–20°C; the overall regression (not plotted) is PO2=5.74–0.004V(mit,f) (r2=0.94).

View larger version (10K): [in a new window]   Fig. 6. The relative influence of cell temperature (A) and fibre radius (B) on calculated oxygen tensions in Chaenocephalus aceratus. Circles, mean fibre PO2; plus signs, PO2 standard deviation; triangles, minimum fibre PO2. Input variables were as follows: fibre radius 12.5 µm (A), temperature 15°C (B); common variables were Krogh’s diffusion coefficient (0.4), the number of capillaries (2), mitochondrial volume density (0.2) and capillary radius (2.1 µm).