LEVEL I
MATERIALS
- Rat liver
- Physiological saline (0.85% w/v NaCl)
- 0.25 M sucrose in 10 mM Tris-HCL, pH 7.4
- Brendler teflon homogenizer
- Refrigerated preparative centrifuge
- 0.08 M CaCl in 0.25 M sucrose plus 10 mM Tris-HCl
- 150 mM KCl in 10 mM Tris-HCl Buffer, pH 7.4
- Phase contrast microscope, slides, coverslips
PROCEDURE 4
Decapitate and exsanguinate a rat that has been starved for at least 24 hours prior to the lab. 5
Fill a syringe with saline and gently perfuse the liver by forcing the saline through the hepatic portal vein, and through the liver.
Remove the liver, place it in a preweighed beaker and weigh the beaker and liver. Calculate the weight of the liver.
Prepare a 10% (w/v) homogenate or brei. For each gram of liver, add 9.0 ml of 0.25 M sucrose in 10 mM Tris-HCL, pH 7.4. to the beaker.
Gently chop the liver in the sucrose and transfer the chopped liver to a teflon homogenizer. 6
Gently homogenize the liver while keeping it chilled.
Centrifuge the brei at 12,000 xg for 10 minutes at 4 ° C. Decant the supernatant into a chilled beaker and discard the pellet.
Add 0.08 M CaCl to the supernatant to yield a final concentration of 8 mM (use 1 ml of CaCl per 9 ml of supernatant). Stir gently and recentrifuge at 25,000 xg for 15 minutes at 4 ° C
Carefully remove and discard the supernatant. 7
Resuspend the pellet (containing the lysosomes) in 30 ml of 150 mM KCl in 10 mM Tris-HCl Buffer, pH 7.4.
Re-sediment the lysosomes by a final centrifugation at 25,000 xg for 15 minutes at 4 ° C.
Remove a small portion of the pellet for Exercise 7.2 . Resuspend the remainder of the pellet in 30 ml of 150 mM KCl/10 mM Tris-HCl Buffer. This suspension is the lysosome fraction for Exercise 7.3 .
Prepare a wet mount of the resuspended lysosome pellet and observe with a phase contrast microscope at 100X. Draw any structures observed.
