DR75

DMEM, with high glucose content (Invitrogen, 12100-061)

200 mM glutamine

5000 μg/mL penicillin/streptomycin solution

RS (rat serum; see Preparation of Rat Serum)

Inactivate 10 mL of RS for 30 min at 56°C. Prepare DMEM by adding 10 mL of 200 mM glutamine and 10 mL of 5000 μg/mL penicillin/streptomycin solution to 1 L of DMEM. After the RS is inactivated, add 3.33 mL DMEM to the RS. (Thus, DR75 is made up of 75% RS and 25% DMEM.) Keep any unused DR75 or RS at 4°C, and replace every 7-10 d to prevent any contamination.