Effect of daily oral intake of manganese on free polysomal protein synthesis of rat brain.

The effect of manganese on free polysomal protein synthesis of immature rat brain (3 weeks old) has been determined after 1, 2, 3, and 4 weeks of daily intake of 55 micrograms manganese/ml of drinking water. The protein synthesis was inhibited up to 35% during the first 3 weeks and returned toward the control level during the fourth week of treatment. Cross-incubation experiments with polysomes and pH 5 enzyme fractions indicated that the inhibition of protein synthesis is due to alteration of the pH 5 enzyme fraction. Furthermore, cerebral t-RNA content was reduced by 20% during the first 3 weeks and also returned to the control level after 4 weeks. The data suggest that the previously reported retardation in learning and memory of manganese treated immature rats may partly be due to alteration of cerebral RNA and protein synthesis. It was also evident that an adaptation mechanism to the observed effect of manganese developes after three weeks of daily intake of 55 micrograms manganese/ml.