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Fig. 5. Effect of PO2 on oxygen consumption
(
O2) by hagfish
dorsal aortas (A) and salmon vessels (B).
O2 is tightly
regulated in unstimulated hagfish aortas (filled triangles) between a
PO2 of 15 and 115 mmHg (1 mmHg=0.133 kPa), but
varies with PO2 at either extreme. At a
PO2 of 12 mmHg
O2 falls to 90%
of the regulated level and
O2 is halved at
3 mmHg (P50).
O2 was not
affected by pre-contracting hagfish aortas with 100 µmol
l–1 carbachol (CBC; open triangles).
O2 was also
regulated in unstimulated salmon vessels (B; filled circles) between a
PO2 of 15 and 115 mmHg; however, per unit
tissue mass it was five times greater than that of hagfish aortas.
Pre-treatment of salmon vessels with 100 µmol l–1
carbachol nearly doubled
O2 at all
PO2 (open circles). Mean ± s.e.m.;
N indicates the number of groups of 4–6 vessels per group in
each experiment (standard error not shown when within the symbol). Broken line
shows the PO2 dependency of hypoxic contraction
in hagfish dorsal aortas [redrawn from Olson et al.
(Olson et al., 2001)].
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