Total folate content of erythroblasts in culture. Control (A) and folate-deficient (B) erythroblasts were cultured in either folate-deficient (□) or control medium (▪) and harvested at the times indicated. The total folate concentration was determined by Lactobacillus casei bioassay. Data are the means ± SEM of three experiments. *P < .02 (A) or P < .002 (B) when folate levels are compared between folate-deficient medium and control medium at the respective hours of culture.