Effect of Ovariectomy with and without Replacement Therapy on Calcium Metabolism in Female Albino Rats

Osteoporosis is a chronic, progressive disease of the skeleton characterized by
decreased bone mass due to a reduction in both organic and non organic
components. Women are more likely todevelop the disease, especially
postmenopausal women. The aim of the present workwas to assess the effect of
ovariectomy with or without replacement therapy on calcium metabolism in female
albino rats and the possibility of preventing progression of osteoporosis by means of
hormonal supplementation and to compare the effects of different supplementations.
The present study was done on 90 adult female albino rats that were divided four
weeks after bilateral ovariectomy (OVX) (except the control group) into nine equal
groups as follow: Control group (non-ovariectomized), Ovariectomized group,
Ovariectomized estrogen treated (30 μg/kg/day SC, 8 weeks) group, Ovariectomized
progesterone treated (10 mg/kg/day SC, 8 weeks) group, Ovariectomized estrogen (25
μg/kg/day SC, 8 weeks) and progesterone (10mg/kg/day S.C., 8 weeks) treated group,
Ovariectomized calcium treated (70 µL/day – calcium gluconate 0.24gm/ml- orally, 8
weeks) group, Ovariectomized calcitonin treated (10 IU/kg SC, 8 weeks) group,
Ovariectomized calcitonin and calcium treated group, Ovariectomized vitamin D
treated (0.5µg/kg orally, 8 weeks) group. Blood samples were collected, centrifuged
and used for determination of calcium, phosphorous, parathormone and calcitonin
serum levels. The left femur of each rat was removed, cleaned, weighted in air and in
water and the bone density was determined. Fat-free dry femurs obtained by
extracting the femurs for 48 h in 90% petroleum ether and dried in a forced-air oven
at 90
0
C until constant weight was obtained. The bone ash weight which contains the
minerals was obtained after ashing at 600
0
C for 24 h. On the basis of the obtained
weights the percentage of organic and non-organic components were calculated.
The results obtained revealed that ovariectomy produced a significant reduction
in bone mineral density (BMD), dry weight, ash content, femoral calcium content and
organic matrix weight compared to the control group, indicating that there was a
decrease in bone mass rather than a decrease in bone minerals. Serum calcium
concentration did not show any significant change following OVX, serum calcitonin
level decreased after OVX and increased with estrogen supplementation. The
combination groups which were supplemented either with (estrogen and
progesterone) or with (calcitonin and calcium)-with insignificant differences between
them- increased BMD, dry weight, ash content, organic matrix weight and ash
calcium content. The percentage changes in BMD were 18% and 17.3% in these
groups respectively as compared to the ovariectomized group. Calcitonin decreased
serum calcium level, increased partially BMD and increased significantly bone dry
weight, organic matrix weight, ash content and ash calcium of left femur, compared
to OVX group. The calcium supplemented ovariectomized group had insignificant
difference with the ovariectomized group in all femur parameters. When it wss
compared with the control group, there was a significant reduction in BMD. This
finding could be explained that, calcium deposition in bone could be dependent on
calcitonin level which was decreased by ovariectomy. So, calcium potentiates the
effect of calcitonin on bone mass that ovariectomized calcitonin and calcium treated
female group had better effect on bone mass than calcitonin therapy alone. The bone
mass was greater by 16.31 % in vitamin D treated ovariectomized group, 15.96% in
both estrogen and calcitonin treated ovariectomized groups and 15.6% in
progesterone treated ovariectomized group when compared to OVX group. There was
a significant higher serum phosphorus concentration in ovariectomized group
compared to the control group, while other ovariectomized treated groups had serum
phosphorus concentrations that were similar to those of the control group. There was
an insignificant change in serum parathormone levels in the ovariectomized and the
ovariectomized treated groups compared with the control group.
In conclusion,the present study showed that the combination therapy either with
estrogen and progesterone or with calcitonin and calcium was found to be the most
effective treatment regimen in OVX rats.