Evidence for dramatically increased bone turnover in spontaneously hypertensive rats

Abstract

Using the 3H-tetracycline model, whole-body skeletal bone resorption was compared among male and female spontaneously hypertensive (SHR) rats and normotensive Wistar Kyoto (WKy) and Sprague-Dawley (SD) rats. Immature animals undergoing rapid skeletal growth and bone sculpting showed a tendency for decreased indices of skeletal resorption in females compared with males. By 24 weeks of age, the indices of the rate of resorption and extent of metabolically reactive bone in male rats were decreased a mean of 68% and 74%, respectively, compared with values obtained at 8 weeks. By comparison, values for 24-week-old females decreased only 26% and 56%, respectively, evidence for a significantly elevated level of resorptive activity in mature females compared with males in each of the 3 rat strains. Within-sex comparisons of 24-week-old animals indicated that bone resorptive activity was similar between normotensive male and normotensive female groups. By comparison, the resorptive activity was significantly increased in both male and female hypertensive rats compared with normotensive controls. This condition was exaggerated in female hypertensive rats, which showed an approximate 81% and 44% increase in the indices of rate of resorption and extent of metabolically reactive bone compared with normotensive WKy controls. The results indicate a marked sexual dichotomy in the decline of skeletal bone resorptive activity following maturation and slowing of skeletal growth. They further indicate a significant elevation of whole skeleton bone turnover in male SHR rats and dramatically increased bone turnover in female SHR rats.