| Objective: To explore the osteocalcin (OC),alkaline phosphatase (AP),carboxyterminal propeptide of type I procollagen(PICP), and analyse the relationship between bone marker and longitudinal bone growth. And choose the serological indicators for longitudinal bone growth.Methods: Choose twenty 3-week-old male weanling SD rats. They were randomly divided into two groups: the dexamethasone group(n=12) and the control group(n=8). According the formula dB=dA·RB/RA·(WA/WB) 1/3 in the book which named"animal experiments method"calculate the required dose of dexamethasone in rats. dB is the required dose of per kilogram of rats and dA is the dose of the human. WA is the standard weight of human and WB is the standard weight of rat. RA , the shape index of human, is 0.1. RB, the shape index of rat, is 0.09. The dose of dexamethasone is 0.15-0.3mg/kg in human, caculate the rat's dose is 100-200μg/100g. The dose of dexamethasone we choosed is 200μg/100g in our experment. The rats in the dexamethasone group received dexamethasone(200μg/100g) for 10 days.The rats in the control group received matching volume sodium chloride solution. All rats were weighed everyday. The rats were killed by using 10% chloral hydration. The length of nose-tail were measured and the venous blood were collected. The rat tibiae were separated, and the length were measured. The proximal tibiae were excised, fixed and decalcifide. After paraffin embedded, five-micron paraffin sections were cut. Tibiae were fixed overnight at 4℃in 3.8% formalin and decalcified in 15%EDTA for two weeks. Then fixed the tibiae in 4% paraformaldehyde. Tissue blocks were dehydrated in ascending series of ethanol(70%, 80%, 90%, 95%, 100%), cleared in xylene and embedded in paraffin. Five-micron paraffin sections were cut. The growth plate sections were stained by histochemisty methods, including Van Gieson stain, Masson's trichrome, Mallory's trichrome. The total thickness of growth plate, the extent of the proliferation zone and hypertrophy zone were measured by using the image analysis system of Leica Qwin. The concentration of serum OC, AP, PICP were assayed. The data were analyzed by SPSS 16.0 statistic software and expressed with mean±standard deviation. The difference between groups were analyzed by independent-sample T test. The correlation was analyzed by Pearson method.Results:1 The body weight, the length of nose-tail and tibiae, the total thickness of growth plate, the extent of the proliferation zone and hypertrophy zone were 97.71±8.95 g, 27.82±1.03 cm, 28.94±1.17 mm, 4.01±0.28μm, 1.98±0.13μm, 1.67±0.18μm in the dexamethasone rats;and 127.87±12.68g, 30.29±0.97cm, 30.54±1.06mm, 5.53±0.46μm, 2.25±0.30μm, 2.86±0.19μm in control group . There were significant differences between two groups(P<0.05).2 The serum OC, AP, and PICP were 0.48±0.15 ng/ml, 80.18±19.47 U/L, 42.67±12.06 pg/ml in the dexamethasone group, and 0.46±0.16 ng/ml, 76.60±1.69 U/L, 37.57±16.98 pg/ml in control group . There were no significant differences between two groups(P>0.05).3 There was negative correlation between the extent of hypertrophy zone and the serum AP in the dexamethasone group (r=-0.605,p=0.037).4 There was positive correlation between the serum PICP and the length of nose-tail (r=0.725,p=0.042). The weight (r=0.820,p=0.013), too.5 There was negative correlation between the serum AP and PICP in the dexamethasone group (r=-0.605,p=0.037).6 There was significant positive correlation between the serum OC and PICP in the control group (r=0.868,p=0.005).Conclusion: 1 Glucocorticoid inhibit the longitudinal bone growth. 2 The inhibition of glucocorticoid to the osteoblasts of growing rats is not obvious. 3 PICP may be a potential marker for the longitudinal bone growth. |
