Changes of 1,25 dihydroxyvitamin D levels in ovariectomy female rats after Nilestriol treatment

Objective To study the changes of renal vitamin D metabolism and skeleton phenotypes in ovariectomized rats and effects of estrogen treatment. Methods Female SD rats(n=30) were randomly divided into 3 groups(n=10 for each).Bilateral ovariectomy for ovariectomy(OVX) and OVX-estrogen(OVX-E) groups,and sham surgery for SHAM group were performed at 6 month of age respectively.Meanwhile,estrogen(1 mg/kg Nilestriol in 2 mL drink water) in OVX-E group was administered twice a week by gavages from 6 to 18 weeks after operation.Same volume of drink water was used as the control for OVX and SHAM groups.The serum vitamin D levels,calcium and phosphate,and skeleton phenotypes were investigated at the middle or end of experiments. Results The serum 1,25(OH)2D level in OVX rats was 63.1 pmol/L,increased by 64%(P0.001) compared with 38.5 pmol/L in SHAM.The high 1,25(OH)2D level was back down to 24.7 pmol/L by estrogen treatment in OVX-E(-60.8% versus OVX,P0.001),which was lower than that in SHAM(P0.01).The osteoporotic phenotypes in OVX rats were showed by the decrease(-9.5% in femur,P0.001 and-9.8% in lumbar,P0.001) of volume bone mineral density(vBMD),and the decrease of bone volume as determined by histomorphometry analysis.Bone resorption was activated after ovariectomy as showed by the increased urine PyD excretion(58.7%,P0.05).Meanwhile,the calcium levels in serum and urine of OVX rats were lower than that in SHAM.The skeleton phenotypes were improved by Nilestriol treatment showed by increased vBMD and bone volume,increased serum calcium and decreased urine PyD excretion,while the urine Ca excretion still kept in lower level(-60%,versus SHAM,P0.01). Conclusions The serum 1,25(OH)2D level was increased in ovariectomized osteoporotic rats,which was fell down by estrogen treatment along with improved bone quality and structure.