TY - JOUR
T1 - Aromatase activity in microsomal preparations of human genital skin fibroblasts
T2 - Influence of glucocorticoids
AU - Berkovitz, Gary D.
AU - Bisat, Tarek
AU - Carter, Kathryn M.
N1 - Funding Information:
Acknowledgements-We thank MS Kathy Klein for her excellents ecretariaal ssistancea nd Mrs Shirley Ho for her technicala ssistance. This work was supportedi n part by USPHS Research Grants ROI-DK-35339 and ROI-DK-00180.
PY - 1989/9
Y1 - 1989/9
N2 - Skin is an important site of estrogen production in men. Although the aromatase complex in these cells appears to be similar to that of other human cells, the regulation of aromatase by glucocorticoids in cultured human skin fibroblasts is unique. We examined aromatase activity in microsomal-enriched fractions of cultured human skin fibroblasts in order to characterize better the factors that regulate the aromatase in these cells. The optimum pH for aromatase activity in microsomal preparations ranged between 7.0 and 7.5. When androstenedione was the substrate, the mean Vmax was 0.58 pmol/mg protein/h (range: 0.09-1.26 pmol/mg protein/h) and the mean Km was 27 nM (range: 9-50 nM). When aromatase activity was determined as a function of NADPH concentration, the mean Vmax was 0.39 pmol/mg protein/h (range 0.11-0.82 pmol/mg protein/h) and the mean Km., was 180 μM (range: 86-300 μM). For skin fibroblasts exposed to DEX, aromatase activity in isolated microsomes and intact cells was stimulated demonstrating a typical time course with peak levels at 14 h and a decline toward baseline with prolonged (48-60 h) exposure. Cytosol from DEX-stimulated cells did not stimulate the aromatase activity in microsomal-enriched preparations from untreated cells. In addition, cytosol from cells incubated with DEX for a prolonged period (60 h) did not inhibit the higher aromatase activity of microsomes from cells incubated with DEX for only 14 h. We previously demonstrated that skin fibroblasts incubated with DEX and CHX produced a superinduction phenomenon for aromatase activity. This superinduction of enzyme activity also occurred in the microsomal-enriched fraction and was unaffected by the cytosol of these cells. These studies exclude the possibility that the unique effects of DEX on the aromatase in human skin fibroblasts are due to the production of either inhibitory or stimulatory soluble factors within cytosol.
AB - Skin is an important site of estrogen production in men. Although the aromatase complex in these cells appears to be similar to that of other human cells, the regulation of aromatase by glucocorticoids in cultured human skin fibroblasts is unique. We examined aromatase activity in microsomal-enriched fractions of cultured human skin fibroblasts in order to characterize better the factors that regulate the aromatase in these cells. The optimum pH for aromatase activity in microsomal preparations ranged between 7.0 and 7.5. When androstenedione was the substrate, the mean Vmax was 0.58 pmol/mg protein/h (range: 0.09-1.26 pmol/mg protein/h) and the mean Km was 27 nM (range: 9-50 nM). When aromatase activity was determined as a function of NADPH concentration, the mean Vmax was 0.39 pmol/mg protein/h (range 0.11-0.82 pmol/mg protein/h) and the mean Km., was 180 μM (range: 86-300 μM). For skin fibroblasts exposed to DEX, aromatase activity in isolated microsomes and intact cells was stimulated demonstrating a typical time course with peak levels at 14 h and a decline toward baseline with prolonged (48-60 h) exposure. Cytosol from DEX-stimulated cells did not stimulate the aromatase activity in microsomal-enriched preparations from untreated cells. In addition, cytosol from cells incubated with DEX for a prolonged period (60 h) did not inhibit the higher aromatase activity of microsomes from cells incubated with DEX for only 14 h. We previously demonstrated that skin fibroblasts incubated with DEX and CHX produced a superinduction phenomenon for aromatase activity. This superinduction of enzyme activity also occurred in the microsomal-enriched fraction and was unaffected by the cytosol of these cells. These studies exclude the possibility that the unique effects of DEX on the aromatase in human skin fibroblasts are due to the production of either inhibitory or stimulatory soluble factors within cytosol.
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U2 - 10.1016/0022-4731(89)90322-1
DO - 10.1016/0022-4731(89)90322-1
M3 - Article
C2 - 2779225
AN - SCOPUS:0024385223
VL - 33
SP - 341
EP - 347
JO - Journal of Steroid Biochemistry and Molecular Biology
JF - Journal of Steroid Biochemistry and Molecular Biology
SN - 0960-0760
IS - 3
ER -