Effect of maternal dietary zinc on growth and mitogenic responsiveness in suckling mice

The effects of varied levels of maternal dietary zinc on growth and immunological development of suckling A/J mice were studied. From 5 days postpartum, lactating dams were fed biotin-fortified egg-white diets containing the following levels of zinc: 1.6 microgram/g (low zinc), 3.6 microgram/g (intermediate zinc), 5.8 microgram/g (moderate zinc) and 30 microgram/g (control). At 17 days of age, low zinc pups exhibited reduced body weight gain (70%), smaller thymuses and spleens, and reduced splenocyte numbers (18%). Intermediate zinc pups had normal body weights but slightly reduced spleens and thymuses; moderate zinc pups were unaffected. Since suckling mice are not fully immunocompetent, splenic mitogenic responses to phytohemagglutinin (PHA), concanavalin A (Con A), lipopolysaccharide (LPS), pokeweed mitogen (PWM), and dextran sulfate (Dx) were used to evaluate the status of various lymphocyte subpopulations. Neonates from the low zinc group gave no Con A response and limited responses to LPS and PWM (50%). Intermediate zinc pups responded satisfactorily to all mitogens except LPS (64%); moderate zinc pups responded normally. It was concluded that 5.8 microgram/g maternal dietary zinc, fed day 5-17 postpartum, is adequate for normal neonatal growth and mitogenic responses. Conversely, 1.6 microgram Zn/g caused neonatal growth retardation and reduced mitogenic responses without excessive mortality.