Delvalle J A, Greengard O
Pediatr Res. 1977 Jan;11(1 Pt 1):2-5.
The mean value of phenylalanine hydroxylase activity in adult human liver was almost twice as high as that in the fetal ones; no consistent variations were seen with sex, fetal age (between the 11th and 22nd week of gestation), or with hours between delivery and death. The tyrosine aminotransferase levels did not correlate with sex, age, or method of abortion; however, they were 5 times higher in the two fetuses which survived for more than 1.5 hr after delivery. The mean concentration of tyrosine aminotransferase (excluding these two fetuses) was about 15 times lower than in the adult liver. Phenylalanine hydroxylase is known to appear in rat liver on the 20th to 21st day of gestation. Tyrosine aminotransferase, on the other hand, emerges on the first postnatal day and, as shown here, can be evoked by premature delivery. Thus, in man as in the rat, (1) phenylalanine hydroxylase approaches physiologically significant levels at an earlier development stage than does tyrosine aminotransferase and (2) extrauterinization stimulates the synthesis of tyrosine aminotransferase but not of phenylalanine hydroxylase. Speculation There is a greater analogy than is usually assumed between human and rat liver with respect to the time schedule of enzymic differentiation and the factors which regulate it.
成人肝脏中苯丙氨酸羟化酶活性的平均值几乎是胎儿肝脏的两倍；未发现其活性随性别、胎龄（妊娠第11至22周之间）或分娩与死亡之间的时间间隔而出现一致变化。酪氨酸转氨酶水平与性别、年龄或流产方式无关；然而，在分娩后存活超过1.5小时的两个胎儿中，其水平高出5倍。酪氨酸转氨酶的平均浓度（不包括这两个胎儿）比成人肝脏低约15倍。已知苯丙氨酸羟化酶在大鼠肝脏妊娠第20至21天出现。另一方面，酪氨酸转氨酶在出生后第一天出现，如此处所示，可由早产诱发。因此，在人类和大鼠中，（1）苯丙氨酸羟化酶在比酪氨酸转氨酶更早的发育阶段达到生理显著水平，且（2）宫外生活刺激酪氨酸转氨酶的合成，但不刺激苯丙氨酸羟化酶的合成。推测在酶分化的时间进程及其调控因素方面，人类和大鼠肝脏之间的相似性比通常认为的更大。
