Changes of tibial morphology due to propranolol medication in ovariectomized rats

Yanling LI; Xiaofeng Lü; Xingguang ZHANG; Qiu ZU

ABSTRACT

BACKGROUND:

Propranolol is a nonselective competitive adrenergic β-receptor blocker capable of suppressing sympathetic nerve excitation. Postmenstrual osteoporosis may be associated with the changes of sympathetic nerve activity.

OBJECTIVE:

To observe the effect of propranolol on tibial morphology in ovariectomized rats, and compare it with that of estrogen medication.

DESIGN:

Completely randomized design and controlled experiment.

SETTING:

End ocrinology Department, General Hospital of Beijing Military Area Command of Chinese PLA.MATERIALS This experiment was conducted at the animal laboratory of the Institute of Basic Theory Research of Traditional Chinese Medicine between March 2002 and April 2003. Forty female unmated SD rats aged 6 months were included and randomized into 4 groups with 10 rats in each group sham-operation group, estrogen medication group, propranolol treatment group, and placebo group.

METHODS:

① Rats in estrogen group, propranolol treatment group and placebo group were anesthetized before the abdomen was opened and bilateral ovaries were excised. Rats in sham-operation group had their abdominal cavity opened and a piece of ovary surrounding fattytissue excised before closing the abdomen. ② Estrogen medication group Rats were given hypodermic injection of grain oil dissolved 17 β-estradiol at a dose of 20 μg/(kg·d). Propranolol treatment group Propranolol was used for gastric infusion at a dose of 18 mg/(kg·d). Placebo group and sham-op-eration group The same volume of grain oil and/or distilled water was used instead of hypodermic injection or gastric infusion. Two treatment groups were given the same intervention as placebo group and sham-operation group during treatment; medication was carried out from postoperative week 1 for altogether 12 weeks. ③ Leica Qwin imaging analysis system was used for morphological measurement of bone tissues so as to calculate the volume percentage, active-surface formation percentage, mineralization rate, and formation rate of bone trabecula. ④ t-test was used for comparing the differences.MAIN OUTCOME

MEASURES:

Comparison of rat tibial morphological parameters between groups.

RESULTS:

Forty rats were divided into four groups with 10 rats in each and all entered the result analysis. ① Left tibial active-surface formation percentage and mineralization rate of bone trabecula They were obviously lower in sham-operation group and estrogen group than in placebo group (P ＜ 0.01), but obviously higher in propranolol treatment group than placebo group (P ＜ 0.05). ② Formation rate of left tibial trabecula It was obviously higher in propranolol treatment group than in placebo group (P ＜ 0.05). ③ The volume percentage of left tibial bone trabecula It was obviously higher in sham-operation group and propranolol treat ment group than in placebo group (P ＜ 0.01), but obviously lower in pro pranolol treatment group than in sham-operation group and estrogen group (P ＜ 0.01).

CONCLUSION:

Propranolol can increase bone mass, reduce bone loss, and promote bone formation in osteoporotic rats following ovariectomy, thus displaying obvious preventive and therapeutic effects on osteoperesis in rats.