Inhibition of L5178Y cells in culture by methotrexate and antibiotics.

Methotrexate, tetracycline, gentamicin, streptomycin, and penicillin inhibited the growth of L5178Y murine leukemia cells in culture with I(50) (concentration of drug that caused a 50% inhibition of growth at 72 h) values of 0.0028 mug/ml (6.2 x 10(-9) M), 7.9 mug/ml, 200 mug/ml, 1,700 mug/ml, and 3,000 mug/ml (5,000 U/ml), respectively. At concentrations achieved clinically or utilized in the laboratory, the antibiotics did not alter the I(50) of methotrexate.