ENZYMATIC O-METHYLATION OF CATECHOL ESTROGENS IN RED-BLOOD-CELLS - DIFFERENCES IN ANIMAL SPECIES AND STRAINS

Enzymatic O-methylation of catechol estrogens in red blood cells has b een investigated with respect to species difference. In the presence o f S-adenosylmethionine, 2- or 4-hydroxyestradiol (2-OHE2 or 4-OHE2) wa s incubated with blood lysate obtained from rats (five strains), guine a pigs, mice, rabbits, dogs, monkeys, and humans, respectively. The yi elded guaiacols and unchanged substrate were determined by gas chromat ography/mass spectrometry in a selected ion monitoring mode employing the corresponding H-2(4)-labeled compounds as internal standards. The total amounts of guaiacols formed from 2-OHE2 and 4-OHE2 were differen t, being the highest (79.6% and 38.1%) in monkeys and the lowest (5.1% and 1.9%) in humans. The ratios of isomeric guaiacols formed from 4-O HE2 (4Me/3Me) were 7.6-71, while those from 2-OHE2 (2Me/3Me) were 1.4- 3.2. Thus, marked differences in O-methylation of catechol estrogens w ere observed among animal species, but no significant strain differenc e was detected in rats.