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甲种胎儿蛋白(甲胎蛋白,a-Fetoprotein,AFP)是胚胎期一种重要的血清特异含糖蛋白质,由一条多肽链组成,分子量为67,000～70,000。胎龄1～2月时,AFP由卵黄囊合成,以后则主要由肝脏合成;胎龄3个月时血清中浓度达最高峰,以后逐渐下降。但5个月前的下降并非由于合成速度下降,而是胎儿的生长速度明显超过AFP的合成速度。8个月后因为出现一种“AFP合成抑制物”,其合成速度才真正下降。AFP的半寿期为3.5～4.0天,出生后,因合成终止,其血清浓度在1～2周内急剧下降,1～2(?)岁时
A fetoprotein (a-Fetoprotein, AFP) is an important serum-specific glycoprotein in the embryonic stage and consists of a polypeptide chain with a molecular weight of 67,000 to 70,000. At 1 to 2 months of gestational age, AFP is synthesized by the yolk sac and later synthesized mainly by the liver. At 3 months of gestational age, the serum concentration reaches the highest peak and gradually declines thereafter. However, the decline of 5 months ago was not due to a decrease in the synthesis rate, but the growth rate of the fetus apparently exceeded that of the AFP. After 8 months, because of the occurrence of a “AFP synthesis inhibitor”, the synthesis rate actually decreased. The half-life of AFP is 3.5 to 4.0 days. After birth, the serum concentration drops sharply in 1 to 2 weeks due to the termination of synthesis, and it is 1 to 2 years old.