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Programme
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The aim of this project, was to establish a small animal model that could provide adequate oxygen delivery at physiological vascular resistance to support studies of metabolism and blood flow in both resting and contracting muscle.
Male Hooded Wistar rats were anaesthetised with sodium pentobarbital
(6mg/100g body weight i.p.). Polyethylene tubing filled with 0.9% heparinised saline
containing 6% w/v dissolved dextran 70 was used as cannulae at all times. The left
carotid artery was cannulated to record mean systemic blood pressure. The right
femoral artery (non-perfused) was cannulated to supply arterial blood to the left
hindlimb femoral artery (perfused) and allow arterial sampling. This loop was passed
through a pump for constant flow with perfused hindlimb pressure recorded via a side
arm pressure transducer distal to the pump. Passive venous return occurred via a
cannula from the left femoral vein to the right external jugular vein, allowing for
venous sampling. The left sciatic nerve was stimulated via a bipolar electrode with
force produced recorded. Blood was sampled from the venous and arterial loops and
oxygen uptake
(
O2)
determined using the Fick equation. Rats were kept
normothermic and were ventilated during experiments to control arterial O2 content.
Extracorporeal blood volume was ≤ 2ml.
At 1 ml⋅min-1 mean systemic pressure was 99.32 ± 4.06 mmHg
(n = 44, mean ± SEM), mean hindlimb perfusion pressure was 92.31 ± 3.08 mmHg.
O2
was 0.328 ±
0.022 μmol-1⋅min-1⋅gww-1
and (a-v)O2diff of 5.03 ± 0.35
ml⋅100ml-1. At 2 ml⋅min-1
with muscle stimulation mean hindlimb pressure was 166.41 ± 5.16
mmHg (n = 8) with a
O2
of 0.570 ± 0.084 μmol-1⋅min-1 ⋅gww-1
and (a-v)O2diff
of 4.44 ± 0.69
ml⋅100ml-1.
O2
is decreased at higher flow rates without
stimulation (0.190 ± 0.02 μmol-1⋅min-1⋅gww-1) but with muscle contraction was
increased. The Table summarises the blood profile during both flow rates.
| Arterial | Venous | 1ml/min | 2ml/min + stim | |
| pH | 7.37 ± 0.01 | pH | 7.27 ± 0.01 | 7.29 ± 0.01 |
| pCO2(mmHg) | 34.77 ± 0.72 | pCO2(mmHg) | 51.44 ± 1.11 | 50.60 ± 1.45 |
| pO2 (mmHg) | 101.47 ± 1.31 | pO2 (mmHg) | 46.33 ± 1.49 | 45.40 ± 2.52 |
| Hct (%) | 45.41 ± 0.42 | Hct (%) | 47.11 ± 0.42 | 49.75 ± 0.92 |
| K+ (mmol/l) | 3.65 ± 0.04 | K+ (mmol/l) | 3.33 ± 0.05 | 3.70 ± 0.05 |
| Hb (g/dL) | 14.80 ± 0.14 | Hb (g/dL) | 15.37 ± 0.14 | 16.26 ± 0.31 |
| SO2 (%) | 97.57 ± 0.10 | SO2 (%) | 71.22 ± 1.77 | 71.69 ± 3.71 |
The development of an autoperfused rat hindlimb by this laboratory gives rise to a physiologically relevant model to study skeletal muscle function and metabolism.