Tissue & blood collection
Blood collected into a plain or clot-activator tube, left upright to clot for about 30 minutes, spun at about 2,000 × g for 10 minutes, and the serum taken off without disturbing the clot.
Our ruleSimulations prepare you for the bench but don't replace hands-on practice.
Serum separation
Blood collected into a plain or clot-activator tube, left upright to clot for about 30 minutes, spun at about 2,000 × g for 10 minutes, and the serum taken off without disturbing the clot.
How it differs from the standard method
- Avoid squeezing the vein: it causes haemolysis.
- Do not spin before the clot forms.
- Process within an hour or two unless the analyte is known to be stable.
1A sample is only as good as its collection
Blood and tissue start to change the moment they leave the circulation: cells keep metabolising, red cells lyse, RNases and proteases go to work and hypoxia switches on stress genes. Good collection is about taking the right amount, by a method the animal tolerates or under adequate anaesthesia, and stabilising it fast enough that the measurement still reflects the living animal.
Serial blood sampling
Small samples from a superficial vein over hours or days, within a limit set by the animal's circulating volume.
Perfusion-fixation
Under deep terminal anaesthesia, saline then fixative are pumped through the heart to clear and fix every organ from inside.
Necropsy
Terminal blood, then organs harvested, weighed and split for frozen and fixed samples.
2How much blood can be taken
A rodent's circulating blood volume is about 7% of its body weight: roughly 1.8 mL in a 25 g mouse. Widely used guidance allows about 7.5% of that as a single sample with a week to recover, and about 10% in total for several samples within 24 hours, followed by two weeks before more is taken.
3Serum, perfusion and the clock
Serum is what remains when blood has clotted: it needs about 30 minutes at room temperature before a 10-minute spin, and squeezing a vein, spinning too early or leaving blood standing for hours all lyse red cells and turn the serum pink. In perfusion, the needle must sit in the left ventricle with the right atrium cut for outflow, at a rate close to the animal's own cardiac output, and the switch to fixative waits until the liver has blanched.
4The 3Rs in this procedure
Tissue that already exists
Use banked samples, tissue shared from other studies, or cells and organoids where they answer the question, before planning a new collection.
One animal, every sample
Plan all analyses before the procedure so one terminal collection yields every tissue and aliquot needed, and microsampling replaces satellite groups for time courses.
Within volume limits, under anaesthesia
Keep blood removal within published limits for the recovery interval, apply pressure to prevent further loss, and do terminal collections under deep anaesthesia confirmed before the first incision.
Key terms
Practise these as flashcards →About 7% of body weight in rodents (≈ 72 mL/kg in mice); the basis of every blood-sampling limit.
Collecting 10–30 µL per time point, so serial samples stay within volume limits.
Rupture of red cells, which colours serum pink and interferes with many assays.
Serum is the fluid after clotting; plasma is from anticoagulated blood and still contains clotting factors.
Flushing the circulation through the left ventricle, usually followed by fixative, under deep terminal anaesthesia.
A 1–10 score of RNA degradation; above about 7 is usually needed for expression work.
Time from loss of blood supply to stabilisation of a sample, during which it degrades.
When to use it
- Pharmacokinetic or biomarker time courses from small serial blood samples.
- Brain and other tissues for histology or immunostaining where blood must be cleared and fixation must be uniform.
- End-of-study collection of blood, organ weights and paired frozen and fixed samples.
Compared with alternatives
Dosing comes first in most studies; blood sampling then measures what the dose achieved.
Immersion fixation of dissected pieces, the alternative to perfusion, and how fixed tissue is processed for sectioning.
What happens to the frozen pieces next; it cannot rescue RNA that degraded before freezing.
Sub-techniques
Choosing one here switches the whole page, including the protocol and the lab, to it.
Blood collected into a plain or clot-activator tube, left upright to clot for about 30 minutes, spun at about 2,000 × g for 10 minutes, and the serum taken off without disturbing the clot.
- Avoid squeezing the vein: it causes haemolysis.
- Do not spin before the clot forms.
- Process within an hour or two unless the analyte is known to be stable.