Study On Ovariectomy Affects The Bone Metabolism Of Rats

After menopause, the function of ovary is decreased, the secretion of estrogen isdescended. The short of estrogen affects bone metabolism through a variety of ways.It is controversial about the representation that the estrogen affects the bonemetabolism, such as bone turnover, bone calcium, bone mineral density and bonestrength. Futhermore, it lacks a systematic research. Therefore, ovariectomized ratwas the object of our experiment, used it to study the representation of the estrogenaffects the bone metabolism.Objective: To study the mechanism and the influence of ovariectomy on the bodyweight, visceral fat, bone mineral density and bone strength.Methods: Forty five female Sprague Dawley rats,255±8.6g, were randomly dividedinto3groups: sham operation group(Sham,n=15), ovariectomized group (Ovx,n=15),ovariectomized plus estrogen group (Ovx+E2, n=15). Ovariectomized (Ovx) andovariectomized plus estrogen group (Ovx+E2) were removed bilateral ovaries, thesham operation group underwent open surgery, not removed bilateral ovaries. Twoweeks after the operation,ovariectomized plus estrogen group (Ovx+E2)was givengavage complement estradiol valerate suspension with amount of1ml/100g*d, thesuspension concentration was0.08mg/ml, ovariectomized group and sham operationgroup was given daily gavage complement saline with amount of1ml/100g. weighedthe rats every week. Feeding three months after surgery, the rats were sacrificed bydecapitation, collected the serum and bilateral fermur, measured the weight of visceralfat， the left femur’s bone calcium, bone mineral content, area, bone mineral density,weight, length, the right femur’s bone strength, the activity of serous alkalinephosphatase, tartrate resistant acid phosphatase and osteocalcin. Results: After operated one week, ovariectomized group’s body weight was higherthan the sham operation group, and kept this trend until the feeding end; the secondweek after operation, ovariectomized plus estrogen group’s weight started to descend,and the weight was lower than the ovariectomized group at the week13after theoperation. The weight of visceral fat in ovariectomized group was higher than thesham operation group and the ovariectomized plus estrogen group; the ratio of thevisceral fat and body weight in the ovariectomized plus estrogen group was lowerthan the ovariectomized group. The left femur’s bone calcium in the ovariectomizedgroup was lower than the sham operation group and the ovariectomized plus estrogengroup; there was no difference between three groups about the left femur’s bonemineral content; the ovariectomized group and the ovariectomized plus estrogengroup’s distal of the left femur’s bone mineral density were lower than the shamoperation group, the whole and middle of left femur’ bone mineral density betweenthree groups were no differences. The whole area of the left femur in theovariectomized group was higher than the sham operation group and theovariectomized plus estrogen group. There were no differences between three groupsabout the left femur’s weight, length and right femur’s bone strength. Both of theactivity of the alkaline phosphatase and tartrate resistant acid phosphatase inovariectomized group were higher than the sham operation group; the level of serumosteocalcin in the ovariectomized group and ovariectomized plus estrogen group werehigher than the sham operation group.Conlusions: In our experimental conditions, after ovariectomy:①increased the rat’sbody weight and accumulated the visceral fat, the estrogen suppressed the rise of thebody weight and the visceral fat’s accumulation;②decreased the femur’s bonecalcium, the estrogen suppressed the loss of bone calcium;③decreased the distal offemur’s bone mineral density, the cancellous bone was more sensitive to theovariectomy;④not decreased the femur’s bone strength;⑤caused a high level ofturnover, bone absorption superior to bone formation, the estrogen could suppress the bone loss.