Blood Collection (How to collect blood sample from a mouse?)
Blood collection from mice can be complicated due to the tiny peripheral veins and the small blood volume (1.5 –3 ml). The amount of blood that can be obtained varies, depending on the procedures applied and whether the mouse will be sacrificed. Up to 1 ml blood can be collected if the mouse will be terminated. 0.2 – 0.4 ml blood can be collected repeatedly from tail vein without significantly harming the mouse. The following are the most commonly used techniques:
Tail bleeding
No anesthesia is required. The mouse needs to be warmed up beforehand, then the mouse is immobilized in a restraint device with the tail protruding. The operator holds the tip of the tail of the mouse, clean the tail with alcohol followed by drying up with sterile cotton ball. The vessel in the tail is cut longitudinally alone a vein by a razor blade, or the tip of the tail may be amputated. Blood drops will accumulate on the surface of the tail and can be collected. Apply pressure to the cutting site to stop the bleeding. This procedure provides an adequate blood volume for most analyses (0.2-0.5 ml).
Retroorbital sinus puncture
A mouse is anesthetized lightly by inhalant anesthetics. The operator extrude the eyeball by stretching the upper and lower eyelids open, insert the tip of a microhematocrip capillary tube or of a 200 µl tip attached to pipetteman into the orbit from the medial canthus. Advance the tip toward the side and back of the eyeball with slight rotating for a depth of 3-4 mm. Blood should flow into the tube freely should the sinus be ruptured. A slight withdraw of the tube sometimes enhances blood flow. Once enough blood is collected, withdraw the tube, hold the eye closed until the bleeding stops.
Cardiac puncture
A mouse is deeply anesthetized and placed on its back. (a) The operator inserts a 25-gauge needle vertically to the thoracic cavity through the left fifth intercostals space just beside the sternum, pulls back on the plunger of the syringe while slowly advancing the needle. When blood appears in the syringe, fixes the position of the needle steady and continues to aspirate the blood to expected amount. (b) The operator inserts a 25-gauge needle left lateral to the xiphoid cartilage and direct cranially into the heart through the diaphragm, pulls back on the plunger of the syringe while slowly advancing the needle. When blood appears in the syringe, fixes the position of the needle steady and continues to aspirate the blood to expected amount. Retracts the needle and apply mild pressure to the injection site.