-transparent.png){kind=logo}
This study investigated the effects of estrogens on the induction of cytochrome P-450 by polycyclic aromatic hydrocarbons in primary cultures of chick embryo hepatocytes. Exposure to polycyclic aromatic hydrocarbons, such as 3-methylcholanthrene led to 2- to 3-fold increases of cytochrome P-450. The amount of cytochrome P-450 induced by 3-methylcholanthrene was increased 40-50% when the synthetic estrogen, 17 alpha-ethynylestradiol, was also present. The rate of decay of cytochrome P-450 in the presence of cycloheximide as measured spectrophotometrically was similar in cells previously treated with either 3-methylcholanthrene or 3-methylcholanthrene plus 17 alpha-ethynylestradiol, suggesting that 17 alpha-ethynylestradiol did not affect the stability of the 3-methylcholanthrene-induced cytochrome P-450. In contrast, 17 alpha-ethynylestradiol did not potentiate the induction of cytochrome P-450 by phenobarbital-like inducers, such as 2-propyl-2-isopropylacetamide, as indicated by a lack of increase in both the content of cytochrome P-450 and benzphetamine demethylase activity. The naturally occurring estrogens, 17 beta-estradiol and estrone, and the synthetic estrogen, diethylstilbestrol, did not affect cytochrome P-450 induction by 3-methylcholanthrene, suggesting that the effect of 17 alpha-ethynylestradiol was not mediated via the estrogen receptor. We investigated whether the amount of cytochrome P-450 increased in the presence of 17 alpha-ethynylestradiol was the same or different from that induced by 3-methylcholanthrene. Treatment with 17 alpha-ethynylestradiol alone resulted in a small increase in ethoxyresorufin deethylase activity. The enzymatic activities of 7-ethoxyresorufin and aryl hydrocarbon hydroxylase, when expressed per cytochrome P-450 content, were identical in microsomes from cells treated with either 3-methylcholanthrene or the combination of 3-methylcholanthrene and 17 alpha-ethynylestradiol. The data suggest that the additional cytochrome P-450 induced by the combination of 17 alpha-ethynylestradiol and 3-methylcholanthrene was the same isozyme as that induced by 3-methylcholanthrene alone.
S A Sundstrom, and
J F Sinclair, and
E L Smith, and
P R Sinclair
May 1988,
Molecular pharmacology,
S A Sundstrom, and
J F Sinclair, and
E L Smith, and
P R Sinclair
September 1976,
Science (New York, N.Y.),
S A Sundstrom, and
J F Sinclair, and
E L Smith, and
P R Sinclair
August 1981,
The Biochemical journal,
S A Sundstrom, and
J F Sinclair, and
E L Smith, and
P R Sinclair
March 1999,
Drug metabolism and disposition: the biological fate of chemicals,
S A Sundstrom, and
J F Sinclair, and
E L Smith, and
P R Sinclair
March 1986,
The Biochemical journal,
S A Sundstrom, and
J F Sinclair, and
E L Smith, and
P R Sinclair
March 1995,
The international journal of biochemistry & cell biology,
S A Sundstrom, and
J F Sinclair, and
E L Smith, and
P R Sinclair
October 1998,
The journal of histochemistry and cytochemistry : official journal of the Histochemistry Society,
S A Sundstrom, and
J F Sinclair, and
E L Smith, and
P R Sinclair
May 1985,
Archives of biochemistry and biophysics,
S A Sundstrom, and
J F Sinclair, and
E L Smith, and
P R Sinclair
January 1977,
General pharmacology,
S A Sundstrom, and
J F Sinclair, and
E L Smith, and
P R Sinclair
December 1984,
Biochemical and biophysical research communications,
