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Effects of Catechol Estrogens 1 and Catecholamines on Hypothalamic and Corpus Striatal Tyrosine Hydroxylase Activity
Author(s) -
Foreman M. M.,
Porter J. C.
Publication year - 1980
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1980.tb09957.x
Subject(s) - tyrosine hydroxylase , pterin , chemistry , tyrosine 3 monooxygenase , medicine , endocrinology , tyrosine , dopamine , catechol o methyl transferase , catechol , catecholamine , monoamine oxidase , enzyme , estrogen , biochemistry , cofactor , biology , allele , gene
The effects of catechol estrogens on tyrosine hydroxylase activity in hypothalamic and corpus striatal extracts were evaluated. When assayed in the presence of subsaturating concentrations of pterin cofactor, tyrosine hydroxylase activity was depressed by 2‐hydroxyestrone, 2‐hydroxyestradiol, Lnorepinephrine, or dopamine. However, estrone, 17β‐estradiol, 2‐ methoxyestrone, or 2‐methoxyestradiol had no consistent inhibitory effect on tyrosine hydroxylase activity under in vitro conditions. Moreover, a decrease in pterin binding affinity (elevated K m ) in the presence of either catecholamines or 2‐hydroxyestrogens was found. These findings were suggestive of a competitive interaction between catechols and pterin. Catechol estrogens and catecholamines were shown to inhibit both membrane‐bound and soluble forms of tyrosine hydroxylase. The membrane‐bound form of tyrosine hydroxylase, however, was found to have a greater binding affinity (lower K l ) for 2hydroxyestradiol and norepinephrine than did the soluble form. The results of the present study are suggestive of a cytoplasmic effect of estrogen that may be mediated by 2‐hydroxyestrogen and terminated by O‐methylation.