Abstract
Ovariectomized rats received a single injection of 10 microgram oestradiol-17 beta 3-benzoate; 90 min or 19 h after injection, slices of various brain areas were prepared and incubated with tritiated noradrenaline for 30 min. Methylated and non-methylated metabolites of tritiated noradrenaline were determined after chromatographic separation. Nineteen h after administration of oestradiol-17 beta 3-benzoate, the formation of normetanephrine, 3-methoxy 4-hydroxy phenylglycol and 3-methoxy 4-hydroxy mandelic acid was decreased (P less than 0.05) in hypothalamic tissue, whereas that of 3,4-dihydroxy mandelic acid was increased (P less than 0.001). In thalamus tissue a decrease or normetanephrine (P less than 0.005) and an increase of 3,4-dihydroxy mandelic acid (P less than 0.001) were also observed. No conclusive results were obtained with hypophyseal tissue. The present findings suggest that oestrogens reduce the methylation of noradrenaline, probably through a competitive inhibition of the catechol-O-methyl-transferase by 2-hydroxylated oestrogens.
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