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If you are interested in isolation of cardiomyocytes from the large animals such as humans, dogs, sheep, please follow the chunk procedure. Here is the method.

Human cardiomyocytes were isolated by enzymatic digestion as previously described

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Briefly, individual specimens were transferred to ice-cold calcium free Krebs-Ringer saline solution consisting of (in g/L): 7.012 NaCl, 0.402 KCl, 1.332 MgSO

4, 0.55 Pyruvate, 3.603 Glucose, 2.502 Taurine, 2.383 HEPES, 1.286 Nitrillotriacetic Acid; pH = 6.96. Connective and adipose tissue were removed and approximately 500mg of myocardial tissue was minced with razor blades in small cubes (approx. 1-2 mm 3). Then, the tissue pieces were washed with fresh Ca2+-free Krebs-Ringer solution 3 times for 3 min each at 37C. After wash, cardiac tissue was incubated for 25 min in 10ml of Krebs-Ringer solution containing (in g/L): NaCl 7.012, KCl 0.402, MgSO4 1.332, Pyruvate 0.55, Glucose 3.603, Taurine 2.502, HEPES 2.383; pH = 7.4, supplemented with 200 nM CaCl2 and Proteinase type XXIV (0.36mg/ml; Sigma-Aldrich) under gentle agitation. The partially digested tissue was transferred to 10ml of Krebs-Ringer saline supplemented with collagenase type XIV (1mg/ml Sigma-Aldrich). The tissue was incubated thrice with this solution for 10 min each at 37C with gentle agitation. Usually, cardiomyocytes were visible by phase contrast light microscopy after the first incubation step, with the biggest amount of cells after the second incubation step. After each incubation step, the supernatants were transferred to a tube and centrifuged at 600 rpm for 3 min. The pellets were re-suspended in 2-3 mL of Krebs-Ringer solution.

An efficient way to isolate large animal heart will be to get a small section of the part to use I.e left ventricle, right,atrium etc and then superfuse with a collagenase or other appropriate digestive enzymes taking precautions to avoid ischemia and cell death.This will conserve a lot of collagenase as they are usually expensive.

AT THE HEART INSTITUTE UNIV SAO PAULO : ISMAR CESTARI AND IDAGINE CESTARI DO THAT , 

              REGARDS NOEDIR STOLF , MD , PhD