The distribution and excretion of manganese: The effects of manganese dose, l-dopa,and pretreatment with zinc

The biliary excretion and tissue distribution of radiomanganese (⁵⁴Mn) was studied in rats, and the effects of varying the dose of Mn, coadministration of Mn with l-DOPA, and pretreatment with zinc (Zn) were determined. As the iv dose of Mn increased, the percentage of the administered dose (% AD) recovered in bile increased, that in liver decreased slingtly, and that in other tissues remained relatively constant. Synthesis of hepatic metallothionein by 24 hr pretreatment with Zn (10 mg/kg) affected neither the normal biliary excretion of ⁵⁴Mn nor the binding profile of ⁵⁴Mn in the liver cytosol. l-DOPA significantly depressed the biliary excretion of Mn without causing a significant change in the M % AD recovered from liver or other internal organs indicating a possible increase in the Mn content of peripheral tissues such as skeletal muscle and skin. The influence of Mn on the excretion of l-³H]DOPA and its metabolites was minimal. Evidence was not found to support the hypothesis that the chelation of Mn by l-DOPA is an important in vivo mechanism influencing the distribution and excretion of either Mn or L-DOPA.