Wy. Shin et al., Effects of cyclosporin A on sex hormone and estrogen receptor in male rat with special reference to cyclosporin A-induced osteoporosis, YONSEI MED, 41(1), 2000, pp. 61-67
The mechanisms of high turnover bone loss induced by Cyclosporin A (CsA) ar
e not clearly understood. Deficiencies in sex hormones result in high turno
ver osteoporosis, and not only androgen bur also estrogen plays an importan
t role in maintaining bone mass in men. To study whether or not there are a
ny changes in the levels of sex hormones, aromatization, and the expression
of estrogen receptors in CsA-induced osteoporosis, we treated 39 rats with
vehicle, low-dose CsA (5 mg/kg) and high dose CsA (15 mg/kg) for 28 days,
and measured sex hormone levels by radioimmunoassay. Aromatase activities i
n ROS cells and 3T3-L1 cells were determined by measuring the conversion ra
te of H-3-androstenedione into H-3-estrone. ER and ER mRNA were measured by
competitive RT-PCR in collected marrow cells and ROS cells. The levels of
free testosterone in the serum in low-dose CsA-treated rats were unchanged,
but the levels were significantly decreased in those treated with high-dos
e CsA as previously reported. The levels of total estradiol in the serum we
re significantly increased in the low-dose CsA-treated group (5 mg/kg) and
were comparable to levels of the control group in the high-dose CsA-treated
group (15 mg/kg). CsA increased the conversion of H-3-androstenedione ro H
-3-estrone in ROS cells, but not in 3T3-L1 cells. Meanwhile, CsA treatment
did not change the rates of ER or ER mRNA expression in ROS cells or in col
lected bone marrow cells. In conclusion, CsA treatment decreased the level
of free testosterone in the serum, but did not decrease the level of serum
estradiol by enhancing aromatization. High-turnover osteoporosis induced by
clinical dosage CsA treatment may not be caused by lowering the levels of
circulating estrogen or by decreasing the expression of estrogen receptors.