Affiliation:
1. Sumitomo Pharmaceuticals Research Center, 1-98 Kasugade Naka 3-chome, Konohana-ku, Osaka 554, Japan
2. Environmental Health Science Laboratory, Sumitomo Chemical Co. Ltd, 1-98 Kasugade Naka 3-chome, Konohana-ku, Osaka 554, Japan
Abstract
Abstract
Postmenopausal osteoporosis is caused mainly by a deficiency of oestrogen with rapid bone loss. To target oestrogen to the bone effectively, we have synthesized and evaluated the effects of a novel hybrid compound of oestrogen and bisphosphonate, SM-16896. The tissue distribution pattern and pharmacological potential are reported.
Although the affinity for calf uterine oestrogen receptor was very low (IC50: 73.3 μM; 1/25000 of that of 17β-oestradiol (2.84 nM)), SM-16896 showed oestrogenic activity. SM-16896 (1 μM) induced a 4.5-fold transcriptional activity in rat osteosarcoma UMR-106 cells compared with vehicle-treated control, when we used the expression vector for human oestrogen receptor and a CAT reporter plasmid containing an oestrogen-responsive element. The distribution of SM-16896 after a subcutaneous administration to 7-week-old female rats was examined by radioluminography using 3H-labelled SM-16896. At 30 min after the administration, significant radioactivity was detected in the bone. At 24 h after administration, a high level of radioactivity was detected in the bone, but in the uterus it was only at a background level. Daily subcutaneous administration of 0.5 mg kg−1 SM-16896 for 12 weeks (five times per week) to 13-week-old ovariectomized rats suppressed the ovariectomized-induced reduction in bone mineral density. A bone mineral density ratio of 120% was maintained compared with sham-operated rats, whereas a relatively low suppression of uterine weight was observed (about 50% loss compared with sham-operated rats). In the same experiment, the implantation of a 17β-oestradiol time-release pellet (0.25 mg/pellet/90 days) almost completely suppressed the reduction of both the bone mineral density and uterine tissue weight. It is likely that the effect of SM-16896 on bone was due to its oestrogenic activity, since 1.0 mg kg−1 SM-18108, the bisphosphonate moiety of this compound, had no effect on bone in 7-week-old ovariectomized rats.
The results suggest that SM-16896, a bisphosphonate-conjugated oestrogen, showed a preference profile in the uterus and bone due to its characteristic distribution pattern compared with the natural oestrogen analogue 17β-oestradiol. Thus, bisphosphonate-conjugated oestrogens have the potential to improve patient compliance in oestrogen therapy by minimizing adverse effects and reducing the frequency of medication.
Publisher
Oxford University Press (OUP)
Subject
Pharmaceutical Science,Pharmacology
Cited by
21 articles.
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