Banger M, Hiemke C, Haupt M, Knuppen R. Excretion of 2- and 3-monomethyl ethers of 2-hydroxyestrogens in healthy male volunteers. Eur J Endocrinol 1996;135:193–7. ISSN 0804–4643
The formation of catecholestrogens by 2-and 4-hydroxylation of monophenolic estrogens represents a major route of estrogen metabolism. In vitro and in vivo studies on catecholestrogens have shown that 2-hydroxylated catecholestrogens are primarily inactivated by O-methylation, while O-methylation of 4-hydroxylated estrogen is of minor importance. In the present study the in vivo production of isomeric 2- and 3-monomethyl ethers of 2-hydroxyestrogens was measured in 12 healthy omnivorous male volunteers aged 51 ± 4 years. The sum of estrone and 17β-estradiol, 2-hydroxyestrogens (sum of 2-hydroxyestrone and 2-hydroxyestradiol), 4-hydroxyestrogens (sum of 4-hydroxyestrone and 4-hydroxyestradiol) and the sum of the isomeric monomethyl ethers of 2-hydroxyestrone and 2-hydroxyestradiol were measured in 24-h urinary samples. The determinations included hydrolysis of steroid conjugates, separation by chromatographic steps and final quantification by radioimmunoassay. The specificity of the antibodies enabled differentiation between the isomeric monomethyl ethers. The mean urinary excretion rates were 8.8 ± 2.9 μg/24 h for estrone plus estradiol, 5.2 ± 2.4 μg/24 h for the 2-hydroxyestrogens and 1.3 ± 0.5 μg/24 h for the 4-hydroxyestrogens. The 2- and 3-monomethyl ethers of the 2-hydroxyestrogens were found in all individuals, with excretion rates of 5.8 ± 2.6 μg/24 h for 2-methoxyestrogens and 3.6 ± 1.1 μg/24 h for 2-hydroxyestrogen-3-methyl ethers. The findings indicated that 2-hydroxyestradiol is metabolized in vivo by 2-O-methylation and, to a lesser extent, by 3-O-methylation.
Markus Banger, Department of Psychiatry, University of Essen, Virchowstr. 174, 45147 Essen, Germany
Bioequivalence Study of Metoclopramide Hydrochloride 10 mg Tablets in Healthy Male Volunteers