Reproduction Abstracts

Introduction: The peptide hormone insulin-like peptide 3 (INSL3) is a unique product of the developing fetal testis that can be detected at a very early stage of pregnancy in fetal blood and also in the surrounding amniotic fluid from where bidirectional exchange of components can occur as the fetal skin is still not keratinized. To explore inter-fetal transport processes, the pig, as a multiparous species, provides an excellent model.

Materials and methods: Using our modified time-resolved fluorescence immunoassay (ruminant), we assessed INSL3 concentration in blood, amniotic or allantoic fluids of male and female pig fetuses from GD30 onwards and in maternal blood across gestation.

Results and discussion: INSL3 was detected in large amounts uniquely in male fetuses in all fluid compartments from GD45 onwards. Importantly, INSL3 of male fetal origin was also detected in significant amounts in allantoic fluids from female fetuses at GD45, which were directly adjacent to male fetuses in utero. Like amniotic fluid in human and ruminants, allantoic fluid is believed to be largely of fetal origin in pigs. Inter-fetal transport of this male hormone was not evident at later gestational ages, implying that by mid-gestation mechanisms are in place, which support the endocrine autonomy of the pig fetus. Together with our earlier results demonstrating transport of INSL3 between the male fetal calf and its mother, these results show that the early mammalian fetus is vulnerable to endocrine agents from the uterine or maternal environments, and hence also to potential endocrine disrupting substances of relevance for DOHaD.