Methotrexate inhibition of normal trophoblasts in vitro

Methotrexate is a folic acid inhibitor useful in the treatment of gestational trophoblastic disease. Its effect on normal trophoblast in vitro was studied to help establish a minimum effective dose in vivo for the conservative treatment of ectopic pregnancy. In vitro inhibition of normal trophoblastic cell growth was measured after 48 hours of exposure to variable concentrations of methotrexate (10(-2) to 10(-9) mol/L) and rescue with leucovorin. A modification of Cotte's method of trophoblastic cell enrichment was used. Long-term (10 days) linear growth inhibition was observed at concentrations greater than 10(-5) mol/L. Leucovorin control cultures showed no inhibition of cell growth. The study demonstrates that methotrexate is effective in inhibiting normal trophoblastic cell culture growth in vitro at concentrations 1000 times those reported necessary to inhibit deoxyribonucleic acid synthesis in choriocarcinoma cell cultures.