Sansom Institute, and School of Pharmacy and Medical Sciences, University of South Australia, Adelaide, South Australia, Australia.
PLoS One. 2011;6(5):e19821. doi: 10.1371/journal.pone.0019821. Epub 2011 May 16.
The hormone Insulin-like peptide 3 (INSL3) is a major secretory product of the Leydig cells from both fetal and adult testes. Consequently, it is a major gender-specific circulating hormone in the male fetus, where it is responsible for the first phase of testicular descent, and in the adult male. In most female mammals, circulating levels are very low, corresponding to only a small production of INSL3 by the mature ovaries. Female ruminants are exceptional in exhibiting high INSL3 gene expression by the thecal cells of antral follicles and by the corpora lutea. We have developed a specific and sensitive immunoassay to measure ruminant INSL3 and show that, corresponding to the high ovarian gene expression, non-pregnant adult female sheep and cows have up to four times the levels observed in other female mammals. Significantly, this level declines during mid-pregnancy in cows carrying a female fetus, in which INSL3 is undetectable. However, in cows carrying a male fetus, circulating maternal INSL3 becomes elevated further, presumably due to the transplacental transfer of fetal INSL3 into the maternal circulation. Within male fetal blood, INSL3 is high in mid-pregnancy (day 153) corresponding to the first transabdominal phase of testicular descent, and shows a marked dependence on paternal genetics, with pure bred or hybrid male fetuses of Bos taurus (Angus) paternal genome having 30% higher INSL3 levels than those of Bos indicus (Brahman) paternity. Thus INSL3 provides the first example of a gender-specific fetal hormone with the potential to influence both placental and maternal physiology.
胰岛素样肽 3（INSL3）是胎儿和成年睾丸的莱迪希细胞的主要分泌产物。因此，它是男性胎儿中主要的性别特异性循环激素，在胎儿中负责睾丸下降的第一阶段，在成年男性中也是如此。在大多数雌性哺乳动物中，循环水平非常低，这对应于成熟卵巢产生的少量 INSL3。反刍动物的雌性异常之处在于，窦卵泡的膜细胞和黄体中具有高 INSL3 基因表达。我们开发了一种专门的、敏感的免疫测定法来测量反刍动物的 INSL3，并表明，与高卵巢基因表达相对应，非妊娠成年雌性绵羊和奶牛的水平比其他雌性哺乳动物高 4 倍。值得注意的是，在怀有雌性胎儿的奶牛中，这种水平在妊娠中期下降，此时 INSL3 无法检测到。然而，在怀有雄性胎儿的奶牛中，循环母体内的 INSL3 进一步升高，推测是由于胎儿 INSL3 通过胎盘转移到母体内循环。在雄性胎儿血液中，INSL3 在妊娠中期（第 153 天）较高，与睾丸下降的第一腹侧期相对应，并且表现出对父本遗传的明显依赖性，具有纯血或杂种牛的父本基因组（安格斯）的雄性胎儿的 INSL3 水平比父本为印度野牛（婆罗门）的雄性胎儿高 30%。因此，INSL3 提供了第一个具有潜在影响胎盘和母体生理学的性别特异性胎儿激素的例子。
