The distribution and turnover of [3H]AA in proliferating and unstimulated T cells. Splenic T cells, previously cultured as above for 48 hours with (right panel, open circles) or without (left panel, closed circles) anti-CD3 mAb, were labeled with [3H]AA (1 μCi/ml) for 20 min at 37°C. The cells were then washed and cultured at 37°C for up to 60 min in BME with 1% BSA. At the initiation of culture (zero time) and at various times thereafter, cells were harvested, membrane lipids were extracted and free AA and phosphoglycerides were resolved by TLC. The concentration of free [3H]AA and of [3H]AA within different phospholipid molecular species was measured by liquid scintillation counting. Data are the mean and standard error of 4 separate experiments.