To study the effect of calcium ion on aromatization of an androgenic precursor to estradiol by the placenta, cultured term trophoblasts were used as a model system. Secretion of estradiol into the culture medium was regarded as indicating aromatization, since cells cultured with no androgenic precursors produced only insignificant amounts of estradiol. EGTA, verapamil and ionophore A23187 inhib...

The aromatization of androstenedione is inhibited in the presence of aminoglutethimide, diethylaminoethyl-2,2-diphenyl valerate HCl (SKF 525-A), and 1W3 M KCN, but not carbon monoxide or metyrapone. The role of cytochrome P-450 in this reaction could not, therefore, be unequivocally established by inhibition studies. However, it was determined that steroid binding to placental microsomal cytoch...

The aromatization reaction of liquefied petroleum gas has been studied by using three liquefied petroleum gases as raw material and LBO-A as catalyst, and four lump kinetics models networks have been put up on the basis of lump theory and the aromatization reaction mechanism. In the network the aromatization reaction species was firstly lumped into C 4 , propylene, low molecule hydrocarbon, liq...

Aromatization of testosterone in Leydig cells purified from mature rat testes was assessed. Leydig cells incubated for 4 hr with increasing concentrations of [3H]testosterone. At saturating concentrations of testosterone, human chorionic gonadotropin (hCG) acutely stimulated aromatization. This stimulation was first observed at 1 hr, an 8-fold increase being found during a 4-hr incubation. The ...

The significance of in vitro aromatization of [7 alpha-3H]testosterone to estradiol by human breast cancer has been investigated by correlation with (a) estrogen receptor activity and (b) clinical response to endocrine therapy. Evidence for estradiol synthesis was obtained in 66 and estrogen receptor activity in 81 of 110 tumors. Whereas most estrogen receptor-positive tumors synthesized estrad...

The rapid and sensitive assay of lfl,2@3H-androgen aromatization by measurement of ‘HZ0 release (Thompson, E. A., Jr., and Siiteri, P. K. (1974) J. Biol. Chem. 249,5364-5372) has been analyzed to determine its applicability to initial rate studies. It was found that aromatization is the sole reaction catalyzed by lyophilized placental microsomes that causes a loss of tritium from position 1 or ...

Central (central nervous system and pituitary) aromatization appears to be a fundamental process for endocrine control and development. Metabolism of androgens to estrogens and the subsequent metabolism of estrogens have been proven in many species, including humans, and linked to estrogen action. Thus, aromatization appears to initiate or to be involved in activities of importance to endocrine...

Stereospecific nucleophilic substitution at the C-4α position of 2α-chloro-2'(2',6')-(di)halogenopicropodophyllotoxin derivatives with carboxylic acids mediated by BF3·Et2O was described. Interestingly, this stereoselective products were completely controlled by the reaction time. That is, if the reaction time was prolonged to 24.5-31 h, the resulting compounds were all transformed into the unu...

Human aromatase is responsible for the last step of estrogen biosynthesis, for the aromatization of ring A of androstenedione (ASD) or testosterone. In this work the mechanism of aromatization was studied using gas phase and hybrid QM/MM calculations. It is shown that human aromatase can efficiently catalyze the aromatization process via a Compound I (or Compound II) mediated pathway. The natur...