THE METABOLISM OF CATECHOLAMINES IN HYPERTHYROID AND VITAMIN B12 DEFICIENT RATS

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Abstract
The effect of hyperthyroidism and vitamin B12 deficiency was studied on liver monoamine oxidase, liver catechol-O-methyl transferase, and the noradrenaline and adrenaline content of liver, heart, and brain. In the hyperthyroid rats, there was a 25% decrease in liver monoamine oxidase and this decrease does not appear to be related to a decrease in body weight. Liver catechol-O-methyl transferase activity was normal in hyperthyroid animals. The noradrenaline and adrenaline content of liver, heart, and brain were also not modified. Vitamin B12 deficiency did not affect catechol-O-methyl transferase activity but hepatic monoamine oxidase was lower by 20–30% in rats supplemented with the vitamin. In vitro, vitamin B12 and methyl cobalamin did not modify the activity of catechol-O-methyl transferase in concentrations ranging from 1 × 10−3 M to 1 × 10−6 M. Vitamin B12 also did not affect monoamine oxidase activity at concentrations of 1 × 10−4 M to 1 × 10−5 M.