Umon Agata

The Effect of Different Amounts of Calcium Intake on Bone Metabolism and Arterial Calcification in Ovariectomized Rats

Reduced estrogen secretion and low calcium (Ca) intake are risk factors for bone loss and arterial calcification in female rodents. To evaluate the effects of Ca intake at different amounts on bone mass changes and arterial calcification, 8-wk-old female Wistar rats were randomly placed in ovariectomized (OVX) control and OVX with vitamin D3 plus nicotine (VDN) treatment groups. The OVX with VDN rats were then divided into six groups to receive different amounts of Ca in their diets: 0.01%, 0.1%, 0.3%, 0.6%, 1.2%, or 2.4% Ca. After 8 wk of administration, low Ca intake groups with 0.01% and 0.1% Ca diets had significantly reduced bone mineral density (BMD) and bone mechanical properties as compared with those of the other groups, whereas high Ca intake groups with 1.2% and 2.4% Ca diets showed no differences as compared with the 0.6% Ca intake group. For both the 0.01% and 2.4% Ca intake groups, Ca levels in their thoracic arteries were significantly higher as compared with those of the 0.6% Ca diet group, and that was highly correlated with serum PTH levels. An increase in relative BMP-2 mRNA expression in the arterial tissues of the 0.01% and 2.4% Ca diet groups was also observed. These results suggested that extremely low Ca intake during periods of estrogen deficiency may be a possible risk for the complications of reduced BMD and arterial calcification and that extremely high Ca intake may promote arterial calcification with no changes in BMD.

Dehydroepiandrosterone administration increased trabecular mass and dihydrotestosterone levels in the cancellous region of the tibia in young female rats.

The aim of the present study was to determine whether dehydroepiandrosterone (DHEA) administration affects bone mass and local sex hormone levels in the cancellous region of young female rats. Eleven female rats (6 weeks old) were randomly divided into 2 groups: control rats (CON, n=5) and rats treated with DHEA (DHEA, n=6). DHEA dissolved in sesame oil was administered to the DHEA group intraperitoneally at 20 mg DHEA/kg body weight, and the CON group was treated with vehicle only (sesame oil, 0.5 ml). The rats were treated with DHEA or vehicle for 3 consecutive days, followed by 1 day of no treatment. The experimental period was 8 weeks. According to dual-energy X-ray absorptiometry and high-resolution microcomputed tomography data, the DHEA group exhibited increased trabecular bone mineral density (BMD), bone volume, and tibial thickness compared to the findings in the CON group, whereas no effect was observed on cortical BMD or morphometry. The concentrations of free testosterone and estradiol in the cancellous region of the tibia did not differ between the 2 groups, but the DHT concentration was significantly higher in the DHEA group than in the CON group. These findings suggest that an increase in local DHT levels may stimulate an increase in trabecular bone mass during growth phases in female rats.