Changes in peripheral blood cells in mice after injection with benzo(a)pyrene during pregnancy

Pregnant C3H/Anfcum mice were injected ip with 150 micrograms benzo(a)pyrene (BP)/g body weight at the second trimester (12 days). Quantitative and differential changes were assayed in the peripheral blood leukocytes and erythrocytes at various times before and after mating and treatment. Within 5 days after injection, a 2- to 4-fold reduction in leukocytes was observed when compared to controls [corn oil (vehicle for BP)-injected pregnant females] which persisted into the 10th postpartum day. The erythrocytes were also significantly reduced but not to the same degree (1.2- to 1.5-fold). Depression in white blood cells is attributed to lymphocyte depletion since the granulocytes were virtually unchanged and the lymphocyte to granulocyte ratio, ordinarily greater than 2 was 1 or less than one. No change in monocytes was observed and none of the cell populations, including the erythrocytes, appeared to be abnormal (e.g., no increase in reticulocytes). A moderate reduction (1.5-fold) in erythrocytes and leukocytes also occurred in the controls (vs virgin females). Pregnancy also led to transient decreases in medium sized lymphocytes and 3- to 4-fold increase in small lymphocytes shortly after mating to about 3 days before parturition. These results show that, although pregnancy depresses the leukocyte profile, exposure to BP exacerbates this change, and preferentially affects the lymphocytes. These blood profile changes may have important health consequences in the mother and her progeny.