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Query: UNIPROT:P00750 (PLA)
 16,800 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The influence of ethinylestradiol and the three natural estrogens, i.e. estrone, 17-beta-estradiol and estriol, was studied in a melanoma cell line producing a tissue-type plasminogen activator (t-PA). The cell cultures were exposed to the four estrogens by addition of the steroids dissolved in a weak alcoholic solution to the culture media, in which the released t-PA was assayed by an immunoradiometric method. Ethanol (0.76% w/v) stimulated the t-PA production, while no significant effect of the estrogens in the concentration of 1.7 X 10(-7) M was seen. By tenfold increase in estrogen concentration a highly significant reduction of t-PA levels was recorded in the cultures exposed to ethinylestradiol and 17-beta-estradiol. Estriol differed from these two estrogens in having rather weak inhibitory effect; whereas estrone in this concentration had toxic effect on melanoma cells. It was concluded that the present estrogens, in particular ethinylestradiol and 17-beta-estradiol, had a dose-dependent inhibitory effect on the production of t-PA in melanoma cell culture.
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PMID:Estrogen regulation of tissue plasminogen activator in a human melanoma cell line. 308 11

The biological effects of estriol (E3) have been studied in three estrogen targets, namely, the rat uterus in vivo and in vitro, in primary human endometrial cell cultures and in MCF-7 human breast cancer cells in culture. Studies on the temporal relationships between estrogen receptor binding and biological responses in the uterus using estriol and several more long-acting estriol derivatives, namely, 17 alpha-ethynyl estriol, estriol-3-cyclopentyl ether, and 17 alpha-ethynyl estriol-3-cyclopentyl ether, indicate that estriol is a short-acting compound with a brief duration of action. Estriol is a poor stimulator of uterine growth and plasminogen activator activity in vivo. Chemical modifications of the estriol molecule produce long-acting derivatives that result in a prolonged input of hormone receptor complexes into the nucleus and a prolonged and marked stimulation of uterine growth. In human endometrial cells in primary tissue culture, E3 has 12% the affinity of estradiol (E2) for cytosol estrogen receptor and it is quite effective yet slightly less potent than estradiol in stimulation of progesterone receptor synthesis. Low concentrations of E3 (10(-10) M) stimulate growth of MCF-7 cells in vitro and dose-response curves show E3 to be only slightly less effective than E2. In these endometrial and breast cancer cell systems in vitro, there is no metabolism of E3 while E2 is metabolized to estrone. Hence, estriol is an effective estrogen in vitro. In vivo, it is short-acting, but it can be made a full estrogen agonist when given at a sufficiently high concentration or in a chemically modified form which prolongs its activity by enabling effective concentrations of the compound to be maintained in the blood and in target tissues.
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PMID:Biology and receptor interactions of estriol and estriol derivatives in vitro and in vivo. 672 48