AGING-RELATED AND OVARIECTOMY-RELATED SKELETAL CHANGES IN SPONTANEOUSLY HYPERTENSIVE RATS

Background The skeletal impact of estrogen deficiency on subjects with hypertension has not been studied previously, In this study, we exami ned the skeletal characteristics of female spontaneously hypertensive rats (SHR) and their normotensive genetic control Wistar-Kyoto rat (WK Y). We aimed to reveal: 1) the skeletal characters of female SHR, and 2) the response of SHR to ovariectomy (ovx) when compared to WKY and o ther strains, Methods: Undecalcified double-fluorescent labeled cancel lous (proximal tibial metaphysis, PTM) and cortical (tibial shaft, TX) bones from 23-weeks-old, and from rats 2 and 8 weeks post-ovx were st udied, Results: The SHR showed lower body weight, higher heart rate, a nd higher blood pressure than the WKY. Female SHR possessed more perce nt cancellous bone, less net cortical bone, smaller tissue area, and t hinner cortex than WHY. Furthermore, SHR exhibited an age-related canc ellous (-18%) and cortical (-7%) bone loss associated with a decrease in the longitudinal growth rate and bone balance and a decrease in per iosteal bone formation in cortical bone, In contrast, the WRY maintain ed most of these parameters unchanged at their 23-week-old levels. Ova riectomy induced earlier and greater cancellous bone loss in the SHR t han in the WKY, with greater increases in bone turnover rate, eroded s urface, activation frequency, and a decrease in the ratio of labeled t o eroded perimeter in PTM at 2 weeks postsurgery. However, the two gro ups exhibited no differences in bone loss at 8 weeks after ovx in PTM and IX, Conclusions: Spontaneously hypertensive rats were highly sensi tive to estrogen deficiency, This might have clinical relevance to tho se postmenopausal women who suffer from hypertension, in that they may be more susceptible to osteopenia, If so, preventive measures should be initiated sooner than otherwise. (C) 1997 Wiley-Liss, Inc.