Takaya Nitta, Tohru Fukushima, Hiromichi Nakamuta and Masao Koida (*)
Department of Pharmacology, Faculty of Pharmaceutical Sciences, Setsunan
University, Nagaotogecho 45-1, Hirakata, Osaka 573-0101, Japan
(*) To whom correspondence should be addressed.
Abstract: Previously we reported that 8-week treatment with methylprednisolone
acetate (MPA: 0.1 mg/kg, s.c., 3 days a week) of male rats caused a novel
type of osteopenia whose development was prevented by salmon calcitonin
(SCT) in a dose-dependent manner. In this study, to compare the MPA-inducible
osteopenia with the ovariectomy (OVX)-inducible one, female rats were used
instead of male rats and a time-course study of development was made. MPA
treatments for 1, 2, 4 and 8 weeks histologically induced characteristic
osteopenic changes in a time-dependent manner that were histomorphometrically
detectable in tibiae within 4 weeks as reduced bone mass, accelerated bone
resorption, and suppressed bone formation and mineralization. Node-strut
analysis revealed that the connectivity of the trabecular structure remained
unaffected. Such MPA-induced changes in the trabecular structure, to be
defined as thinned-but-uncut, is in a good contrast with OVX-induced unthinned-but-cut
structure, although the latter osteopenic changes became detectable 2 weeks
earlier. Another previous finding confirmed herein was that MPA-induced
osteopenia in female rats was also completely masked by SCT (10 U/kg, s.c.,
5 days a week). The results indicate that the MPA-inducible secondary osteopenic
model in either sex of rats would be usable for testing anti-osteopenic
drugs.
Keywords: Glucocorticoid, Secondary osteopenia, Anti-osteoporotics, Calcitonin,
Ovariectomy