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At least 253 records · Page 14Linked to original sources
PubMed1984

Estrogen induction of progestophilins in rat estrogen-sensitive cells grown in media supplemented with sera from castrated rats and from rats bearing an alpha-fetoprotein-secreting hepatoma.

The purpose of this work was to study the effect of alpha-fetoprotein (AFP) over cell multiplication and the induction of an estradiol-17 beta (E2)-dependent marker, i.e., progestophilins in E-sensitive cells C2(9)RAP derived from a W/Fu rat pituitary tumor. These cells proliferate in isogeneic hosts under the influence of E2, while they proliferate in culture regardless of the presence of E2. C2(9)RAP cells were grown in medium supplemented with 10% horse serum. Progestophilin levels were measured 48 h after adding serum (20% horse, or castrated rat, or AFP-secreting tumor-bearing rat) and estrogen to the 10% horse serum-supplemented medium in which the cells were growing. Maximal induction of progestophilins was obtained at 3 X 10(-10) M E2 in cells grown in medium containing horse or castrated rat serum. In contrast, maximal induction of progestophilins required 3 X 10(-8) M E2 in cells grown in medium supplemented with the serum of Morris hepatoma 7777-bearing rats. This serum contained AFP levels comparable to those present at birth in the rat. 11-Methoxy-17 beta ethynylestradiol (R2858), a synthetic estrogen with little affinity for AFP, was also tested for its ability to induce progestophilins. The degree of maximal induction of progestophilins expressed as percentage of the respective control, was similar for all experimental groups, both with E2 and with R2858. In addition, we compared the free E2 levels in the culture medium with the progestophilin levels and the cell proliferation rate. We found that the progestophilin levels were maximal at free E2 concentrations above 11 pg E2/ml, whereas there was no correlation between the free E2 levels and the proliferation rate. Moreover, the proliferation rate of cells in medium supplemented with horse or castrated rat serum was maximal at concentrations of free E2 below 0.4 pg/ml; whereas cell proliferation was inhibited with hepatoma serum even at concentrations of free E2 of 44 pg/ml. We conclude that the effect of hepatoma serum on the E2 induction of progestophilins seems to be mediated by the effect of AFP on the availability of free estrogen, since it is abolished by the addition of both natural and synthetic estrogens. The inhibitory effect of hepatoma serum upon cell proliferation is not reversed by estrogens and thus seems to be mediated by mechanisms other than E2 trapping by AFP.

Animals↗
PubMed1982

Detection of a heat- and acid-stable 'progesterone'-binding protein in the rat lung.

Using a modified charcoal method, we could detect a steroid-binding component in rat lung cytosol which specifically binds R5020, progesterone, and some of its natural derivatives. The concentration of binding sites is high (30-40 pmol/mg protein), the affinity is moderate, the Kd of the R5020 complex being approximately 10(-7) M. Proteolytic enzymes and sulfhydryl reagents destroyed the binding sites indicating the protein nature and the requirement for disulfide bonds. The protein sedimented in the 2 S range thus had an Mr of 10,000-15,000. Further characteristics are the extreme heat (30 min at 100 degrees C) and acid (pH 1) stability. These properties and the fact that it was not detected in serum, distinguish this binding protein from receptors and specific serum steroid binders.

Animals↗
PubMed1986

Identification of a putative progesterone receptor in the oviduct of a viviparous watersnake (Nerodia).

The steroid hormone progesterone is of particular interest in reproductive tract adaptations associated with the processing of embryonic materials in the evolution of viviparity. To further understand the mechanisms of action of this steroid, a progesterone receptor-like moiety was partially characterized in the oviduct of the viviparous snake Nerodia. Using DNA-cellulose and LH-20 column chromatography, a binding component was identified which exhibits high affinity (KA = 1.5 X 10(9) M-1) and low capacity (approximately 10(-11) M) binding of the synthetic progestin, R5020. In addition, the binding exhibited physiological steroid specificity, and was only identified in reproductive structures considered targets of progesterone action. These characteristics are consistent with the primary characteristics associated with steroid-receptor binding and are similar in both cytosolic and nuclear extract preparations.

Androgens↗