Evidence for dramatically increased bone turnover in spontaneously hypertensive rats

Area of Science:

• Bone Biology
• Endocrinology
• Hypertension Research

Background:

• Skeletal bone resorption is a critical process in bone remodeling.
• Age-related changes in bone turnover differ between sexes.
• Hypertension is associated with altered bone metabolism.

Purpose of the Study:

• To compare whole-body skeletal bone resorption in male and female spontaneously hypertensive (SHR) rats and normotensive Wistar Kyoto (WKy) and Sprague-Dawley (SD) rats.
• To investigate the impact of sex and hypertension on age-related changes in bone resorption.
• To determine the extent of metabolically reactive bone in different rat models.

Main Methods:

• Utilized the 3H-tetracycline labeling model for assessing bone resorption.
• Compared bone resorption indices in immature and mature (8 vs. 24 weeks) male and female rats across three strains.
• Quantified the rate of resorption and the extent of metabolically reactive bone.

Main Results:

• Female rats showed a tendency for decreased skeletal resorption compared to males during rapid growth.
• Mature male rats exhibited significant decreases in resorption rate (68%) and reactive bone (74%) from 8 to 24 weeks.
• Mature female rats showed smaller decreases (26% and 56%), indicating higher relative resorptive activity than males.
• Hypertensive rats (both sexes) had significantly increased bone resorption compared to controls.
• Female hypertensive rats displayed the most dramatic increase in resorption rate (81%) and reactive bone (44%) versus normotensive controls.

Conclusions:

• A significant sexual dichotomy exists in the age-related decline of skeletal bone resorptive activity.
• Whole skeleton bone turnover is elevated in male SHR rats and dramatically increased in female SHR rats.
• Hypertension exacerbates bone turnover, with a pronounced effect in female hypertensive rats.