青春前期双生子血清骨碱性磷酸酶活性测定及遗传度分析

Study on the activity of serum bone alkaline phospbatase and its relations to the heritability among prepuberty Twins

目的通过对青春前期双生子血清骨碱性磷酸酶（bone alkaline phosphatase，BALP）活性的测定，分析血清BALP活性的遗传度，评价特定人群钙的缺乏状况和机体对钙的需求情况。方法调查9～16岁双生子73对，利用骨源性碱性磷酸酶试剂盒进行血清BALP活性测定。在DNA卵型鉴定基础上，以组内相关系数法及Christian遗传度计算公式分析血清BALP活性的遗传度。结果经卵型鉴定，73对双生子中同卵双生子34对，异卵双生子39对；BALP〉250U／L的人占43．1％，BALP为200～250U／L占54．8％，BALP≤200U／L占2．1％；男性中钙摄入不足者占48．4％，女性中占39．0％；各年龄组钙的摄入能满足机体需求的均不到10．0％；尤其是10～13岁年龄段儿童，明确缺钙者所占比例均〉45．0％；不同性别、不同年龄间BALP均值差异无统计学意义，性别t=1．633，P=0．105；年龄F=0．323，P=0．924。经过遗传度分析，单卵双生（MZ）对内方差=191．54，对间方差=1462．22，相关系数=0．77；双卵双生（Dz）对内方差=491．03，对间方差=1475．57，相关系数=0．50；BALP活性的遗传度为0．54。结论青春前期的双生子普遍存在缺钙问题；BALP的活性遗传因素占54％，环境因素占46％。

Objective To evaluate calcium deficiency and demand in pre-puberty twins and to analyze the heritability of serum bone alkaline phosphatase （BALP）. Methods A total of 73 pairs of twins aged 9-16 years were examined by BALP test. Microsatellite polymorphism was used to diagnose the zygosity of twins, while both intraclass correlation coefficient method and Christian formula were performed to investigate heritability of serum BALP. Results The results of zygosity diagnosis displayed that 34 pairs of twins were monozygotic （MZ） twins and 39 pairs were dizygotic （DZ） twins. 97.9 % of the subjects appeared unusual in the activity of BALP, with activity of BALP〉 250 U/L in 43.1% of subjects and 200-250 U/L in 54.8 % of the subjects. The intake of calcium was unsatisfied in 48.4 % of the boys and 39.0% in girls. Less than 10.0% of the subjects were satisfied with the intake of calcium in each age group while over 45.0 % of the subjects in 10-13 age group were deficient in calcium. Differences between the means of BALP in different sex groups （t = 1. 633, P = 0. 105） and different age groups （F = 0. 323, P = 0. 924） were not statistically significant. Heritability analysis displayed that intra-class variation, inter-class variation, intra-class correlation coefficient were 191.54, 1462.22, 0.77 in MZ twins, and those were 491.03, 1475.57, 0.50 in DZ twins respectively with the heritability of BALP activity as 0.54. Conclusion Calcium deficiency is commonplace in pre-puberty twins. Our data showed that the BALP activity was influenced both by genetic （54 96 ） and environmental （46%） factors.