The effect of chlorpromazine on SCE frequency in human chromosomes.

Schizophrenic patients who were receiving, or who had received chlorpromazine showed SCE levels similar to those in a normal control population. Of 8 normal individuals whose lymphocytes were exposed in vitro to chlorpromazine (0.05-2.00 micrograms/ml) for two cell cycles, 4 showed a significant increase in SCE, 3 showed no increase and 1 a decrease compared with untreated lymphocytes. Lymphocytes from a further 8 donors treated with 2.0 micrograms/ml chlorpromazine prior to mitogen stimulation (G0 lymphocytes) showed a similar SCE response. Only 3 of the 8 donors showed a significant increase in SCEs over the baseline level. When proliferating lymphocytes were exposed to chlorpromazine 38 h after culture initiation and prior to the addition of BrdUrd to the culture medium, metaphase chromosomes from only 3 of the 8 individuals studied showed increased levels of exchange. These results indicate that chlorpromazine can induce SCEs in vitro but that there is considerable variation in SCE response among individuals. Furthermore, our data emphasises the importance of using more than 1 or 2 donors when analysing SCE response in human chromosomes.