Influence of maternal age, gestational age and fetal gender on expression of immune mediators in amniotic fluid

ABSTRACT: BACKGROUND: Variations in cytokine and immune mediator expression patterns in amniotic fluid due to gestational age, maternal age and fetal gender were investigated. METHODS: Amniotic fluid samples were obtained from 192 women, 82 with a mid-trimester amniocentesis (median gestational age 17 weeks) and 110 with a caesarean section not in labor (median gestational age 39 weeks). Amniotic fluid was screened by commercial ELISAs for the TH1/TH2/TH17 cytokines and immune mediators IL-1 beta, IL-2, IL-4, IL-6, IL-8, IL-10, IL-12, IL-15, IL-17, TNF alpha, GROalpha, MIP1alpha, MIP1beta, histone, and IP10. Analysis was by Bonferroni correction for multiple comparisons. RESULTS: None of the 15 examined cytokines revealed any differences in expression patterns regarding fetal gender and age of the mothers. Significant differences were found in IL-4, IL-10, IL-12 TNF- alpha and MIP1-beta with respect to gestational age. CONCLUSIONS: Cytokines utilized as biomarkers in the diagnosis of intrauterine infections are not influenced in their expression pattern by fetal gender or maternal age, but may vary with respect to gestational age.     

Maternal LPS induces cytokines in the amniotic fluid and corticotropin releasing hormone in the fetal rat brain

Perinatal infections are a risk factor for fetal neurological pathologies, including cerebral palsy and schizophrenia. Cytokines that are produced as part of the inflammatory response are proposed to partially mediate the neurological injury. This study investigated the effects of intraperitoneal injections of lipopolysaccharide (LPS) to pregnant rats on the production of cytokines and stress markers in the fetal environment. Gestation day 18 pregnant rats were treated with LPS (100 microg/kg body wt i.p.), and maternal serum, amniotic fluid, placenta, chorioamnion, and fetal brain were harvested at 1, 6, 12, and 24 h posttreatment to assay for LPS-induced changes in cytokine protein (ELISA) and mRNA (real-time RT-PCR) levels. We observed induction of proinflammatory cytokines interleukin (IL)-1 beta, IL-6, and tumor necrosis factor-alpha (TNF-alpha) as well as the anti-inflammatory cytokine IL-10 in the maternal serum within 6 h of LPS exposure. Similarly, proinflammatory cytokines were induced in the amniotic fluid in response to LPS; however, no significant induction of IL-10 was observed in the amniotic fluid. LPS-induced mRNA changes included upregulation of the stress-related peptide corticotropin-releasing factor in the fetal whole brain, TNF-alpha, IL-6, and IL-10 in the chorioamnion, and TNF-alpha, IL-1 beta, and IL-6 in the placenta. These findings suggest that maternal infections may lead to an unbalanced inflammatory reaction in the fetal environment that activates the fetal stress axis.     

Oxytocin and vasopressin in the rat do not readily pass from the mother to the amniotic fluid in late pregnancy

In order to see whether the mother contributes to the vasopressin or oxytocin levels of amniotic fluid, these peptides were measured under conditions (1) in which the fetus lacks vasopressin (Brattleboro strain) and (2) where high maternal oxytocin and vasopressin plasma levels were induced by means of a controlled-delivery Accurel-collodion device. No vasopressin could be demonstrated in amniotic fluid of vasopressin-deficient fetuses present in a heterozygous (i.e., vasopressin-synthetizing mother). High peptide levels on the maternal side of Wistar rats generally failed to affect the amniotic fluid levels. The increase that was occasionally seen in amniotic vasopressin was probably due to fetal release concomitant with growth retardation. Amniotic vasopressin is derived from the fetus. Since amniotic fluid oxytocin is neither derived from the mother nor from the fetal brain, other fetal sources should be considered.     

Uterine and serum cytokine arrays in the mouse during estrus

Cytokines govern uterine immunology and embryo receptivity and are increasingly recognized for their embryotrophic roles. While supplementing culture media with cytokines may improve embryo development/viability in vitro, little is known about their physiological profiles in vivo, and hence which are likely to be uterine immunoregulators and embryotrophins. Therefore, this study profiled 23 cytokines in uterine fluid and serum from individual naturally cycling estrous mice. Samples were analyzed by fluid-phase multiplex immunoassays for interleukin (IL)-1, IL-1β, IL-2, IL-3, IL-4, IL-5, IL-6, IL-10, IL-12 (p40), IL-12 (p70), IL-13, IL-17, eotaxin, granulocyte-colony stimulating factor (G-CSF), granulocyte macrophage-colony stimulating factor (GM-CSF), interferon (IFN)-γ, keratinocyte-derived chemokine (KC), monocyte chemoattractant protein (MCP)-1, macrophage inflammatory protein (MIP)-1 MIP)-1β regulated upon activation, normal T-cell expressed and secreted (RANTES) and tumor necrosis factor (TNF)-. There was a marked divergence in cytokine concentrations between uterine fluid and serum. The former was dominated by G-CSF, eotaxin, KC and IL-1, and had significantly higher levels of IL-1β, IL-2, IL-3, IL-4, IL-6, IL-9, GM-CSF, MIP-1, MIP-1β and RANTES. Serum had significantly higher IL-12 (p40), IL-12 (p70), IL-17 and IFN-γ concentrations. No significant differences in IL-5, IL-10, IL-13, MCP-1 or TNF- profiles were noted. These data indicated a strict compartmentalization of uterine cytokines, with G-CSF as a major cytokine at estrous. Results are discussed with respect to immune cell function, post-coital paternal antigen processing, estrous cyclicity, and endometrial angiogenesis, cell turnover and differentiation.     

Prostaglandins in fetal tracheal and amniotic fluid from late pregnant sheep

Concentrations of prostaglandin E (PGE), prostaglandin F (PGF) and 13,14-dihydro-15-keto-prostaglandin F (PGFM) have been measured in fetal tracheal and amniotic fluid from chronically catheterized sheep during late pregnancy. Amniotic fluid contained significantly greater concentrations of these prostaglandins than tracheal fluid (p less than 0.01); there was no correlation between the level of prostaglandins found in each fluid. In tracheal fluid concentrations of PGE and PGFM exceeded those of PGF (P less than 0.01) whereas no significant differences were found in amniotic fluid. The levels of prostaglandins in these fluids were similar in ewes bearing hypophysectomized fetuses.     

Alpha-fetoprotein and albumin in experimentally-induced exencephaly in the rat.

Alpha-fetoprotein and albumin were quantified in the sera and amniotic fluids from control, Vitamin A-treated non-exencephalic and Vitamin A-treated exencephalic rat fetuses. Exencephaly was associated with amniotic fluid alpha-fetoprotein concentrations which were significantly elevated over those of Vitamin A-treated non-exencephalic and of untreated fetuses. Amniotic fluid albumin concentrations also were higher in the exencephalic fetuses than in the non-exencephalic fetuses. Serum alpha-fetoprotein and albumin concentrations were lower in the exencephalic than in the non-exencephalic fetuses. The results are cosistent with simple diffusion across a defective barrier as the cause of elevated amniotic fluid alpha-fetoprotein concentrations in the presence of open neural tube defects. This experimental model of neural tube defects result in changes in amniotic fluid alpha-fetoprotein similar to those changes found in human amniotic fluid alpha-fetoprotein concentrations in the presence of neural tube defects.     

Multiplex bead array assay for detection of 25 soluble cytokines in blister fluid of patients with complex regional pain syndrome type 1

Inflammatory processes are known to be involved at least in the early phase of complex regional pain syndrome type 1 (CRPS1). Blister fluid obtained from the involved extremities displayed increased amounts of proinflammatory cytokines IL-6 and TNFalpha compared with the noninvolved extremities. The aim of this paper is to investigate the involvement of mediators by measurement of several other cytokines using new detection techniques that enable multiple cytokine measurement in small samples. The use of a multiplex-25 bead array cytokine assay and Luminex technology enabled simultaneous measurement of representative (1) proinflammatory cytokines such as GM-CSF, IL-1beta, IL-1RA, IL-6, IL-8, and TNF-alpha; (2) Th1/Th2 distinguishing cytokines IFN-gamma, IL-2, IL-2R, IL-4, IL-5, and IL-10; (3) nonspecific acting cytokines IFN-alpha, IL-7, IL-12p40/p70, IL-13, IL-15, and IL-17; and (4) chemokines eotaxin, IP-10, MCP-1, MIP-1alpha, MIP-1beta, MIG, and RANTES. Although minimal detection levels are significantly higher in the bead array system than those in common ELISA assays, in blister fluid, IL-1RA, IL-6, IL-8, TNF-alpha, IL-12p40/p70, MCP-1, and MIP-1beta were detectable and increased in CRPS1 affected extremities. Levels of IL-6 and TNF-alpha simultaneously measured by ELISA (Sanquin Compact kit) and by multiplex-25 bead array assay (Biosource) were highly correlated (r = 0.85, P < .001 for IL-6 and r = 0.88, P < .001 for TNF-alpha). Furthermore, IP-10 and eotaxin were detectable but diminished in CRPS1, whereas detectable amounts of IL-10 were similar in involved and noninvolved extremities. Multiplex bead array assays are useful systems to establish the involvement of cytokines in inflammatory processes by measurements in blister fluids of CRPS1. Ten representative cytokines were detectable. However, detection levels and amounts measured are at least 3 times higher in the multiplex-25 array assay than in the ELISA assays used simultaneously for the measurement of cytokines.     

Transplantation of amniotic membrane in corneal ulcers and persistant epithelial defects

Amniotic membrane transplantation (AMT) leads to reduction of inflammatory symptoms and causes faster epithelisation in corneal ulcers and persistant epithelial defect. 21 patients with corneal ulcer (n = 18) or non-healing epithelial defect (n = 3) unresponsive to conventional treatment were included in the study. All patients were treated by AMT. Corneal epithelial cells in patients suffering from corneal ulcer secreted 3.51 +/- 1.79 of IL-1alpha, 64.27 +/- 31.53 pg/mL of TNFalpha and 209.07 +/- 201.82 pg/mL of VEGF. Levels of all 3 investigated cytokines were significantly higher as compared to controls (p < 0.005). Amniotic membranes that were used contained 775.69 +/- 613.98 pg/mL of IL-1alpha, 0.036 +/- 0.033 pg/mL of sTNF and 175.01 +/- 166.63 pg/mL of VEGF-R. Supporting effect of the AMT could be explained by the fact that AM secretes its natural antinflammatory antagonists IL-1ra, sTNF and VEGF-R.     

Elevated cerebral spinal fluid cytokine levels in boys with cerebral adrenoleukodystrophy correlates with MRI severity

Background

X-linked adrenoleukodystrophy (ALD) is a metabolic, peroxisomal disease that results from a mutation in the ABCD1 gene. The most severe course of ALD progression is the cerebral inflammatory and demyelinating form of the disease, cALD. To date there is very little information on the cytokine mediators in the cerebral spinal fluid (CSF) of these boys.

Methodology/Principal Findings

Measurement of 23 different cytokines was performed on CSF and serum of boys with cerebral ALD and patients without ALD. Significant elevations in CSF IL-8 (29.3±2.2 vs 12.8±1.1 pg/ml, p = 0.0001), IL-1ra (166±30 vs 8.6±6.5 pg/ml, p = 0.005), MCP-1 (610±47 vs 328±34 pg/ml, p = 0.002), and MIP-1b (14.2±1.3 vs 2.0±1.4 pg/ml, p<0.0001) were found in boys with cALD versus the control group. The only serum cytokine showing an elevation in the ALD group was SDF-1 (2124±155 vs 1175±125 pg/ml, p = 0.0001). The CSF cytokines of IL-8 and MCP-1b correlated with the Loes MRI severity score (p = 0.04 and p = 0.008 respectively), as well as the serum SDF-1 level (p = 0.002). Finally, CSF total protein was also significantly elevated in boys with cALD and correlated with both IL-8, MCP-1b (p = 0.0001 for both), as well as Loes MRI severity score (p = 0.0007).

Conclusions/Significance

IL-8, IL-1ra, MCP-1, MIP-1b and CSF total protein were significantly elevated in patients with cALD; IL-8, MCP-1b, and CSF total protein levels correlated with disease severity determined by MRI. This is the largest report of CSF cytokine levels in cALD to date, and identification of these key cytokines will provide further insight into disease progression and perhaps lead to improved targeted therapies.     

Stimulated cytokine production correlates in umbilical arterial and venous blood at delivery

BACKGROUND: Umbilical venous blood is easy to obtain after delivery, and thus has been commonly used in many studies for cytokine analysis. Our aim was to evaluate whether or not induced cytokine production differs after stimulation in umbilical artery and vein whole blood samples, using two different stimulation protocols. The effect of such stimulation on fetal and maternal blood was also evaluated. METHODS: Blood samples from umbilical artery (UA) and vein (UV), and from the mother were collected from 23 women after delivery at term. Concentrations of cytokines (IL-4, IFN-gamma, IL-6 and TNF-alpha) were measured in plasma and whole blood after PMA/ConA and PMA/ionomycin stimulation. RESULTS: Both in maternal and in fetal samples, cytokine concentrations in unstimulated plasma samples were lower than in stimulated samples, except for IL-4 after PMA/ConA stimulation. UA and UV showed similar, average cytokine levels after stimulation and the correlations were high (r=0.68-0.95). Cytokine concentrations were clearly higher in umbilical blood than in maternal blood after stimulation, but not in plasma. Correlations between maternal and umbilical samples after stimulation were generally low (r<0.41). IFN-gamma was not detectable in unstimulated plasma samples. The production of IL-4 and IFN-gamma was more intense after PMA/ionomycin stimulation than after PMA/ConA stimulation. INTERPRETATION OF THE RESULTS: Concentrations of the cytokines examined are similar in blood from the UA and UV. For IL-4 and IFN-gamma, the stimulant used has a significant effect on the level of cytokine expression, and interestingly, the effect is more pronounced on the fetal than on the maternal side.     

Presence of interleukin 10 in the serum and blister fluid of patients with pemphigus vulgaris and pemphigoid

Interleukin 10 (IL-10) is an immunoregulatory cytokine produced by T lymphocytes and macrophages. Recently, it has been suggested that IL-10 may be involved in the pathogenesis of various inflammatory and autoimmune diseases. Using an ELISA we investigated the presence of IL-10 in the serum and blister fluid of pemphigus vulgaris (PV) patients with active disease and those in prolonged clinical remission compared with normal controls. Sera from patients with bullous pemphigoid (BP), ocular cicatricial pemphigoid (OCP), oral pemphigoid (OP) and blister fluid from five patients with BP were also studied. Increased levels of IL-10 were detected in the sera of 87.5% of patients with active PV and were statistically significant (P=0.0003) when compared with levels in normal human serum. Lower levels of IL-10 were detected in 12.5% PV patients in remission and were statistically significant (P=0.0001) when compared with levels in patients with active disease. Levels of IL-10 were detected in sera of 4.6% (1 of 24) of the normal controls. The levels of IL-10 were approximately four times higher in blister fluids than levels in the serum in the same PV patients. This difference was highly statistically significant (P=0.0008). A correlation was observed between serum levels of IL-10 and titres of pemphigus autoantibodies and with disease severity. Elevated level of IL-10 was detected in the blister fluid from five BP patients. Levels of IL-10 in the sera of patients with BP, OCP and OP were not significantly increased. These preliminary data suggest that IL-10 in concert with other cytokines may play an important role in the pathogenesis of PV and BP.     

Baseline Levels and Temporal Stability of 27 Multiplexed Serum Cytokine Concentrations in Healthy Subjects

BackgroundCytokines are humoral molecules that elicit regulatory function in immunologic pathways. The level and type of cytokine production has become critical in distinguishing physiologic from pathologic immune conditions. Cytokine profiling has become an important biomarker discovery tool in monitoring of the immune system. However, the variations in cytokine levels in individual subjects over time in healthy individuals have not been extensively studied. In this study, we use multiplex bead arrays to evaluate 27 analytes in paired serum samples taken seven days apart from 144 healthy individuals in order to assess variations over a short time period.MethodsFluorescent bead-based immunoassay (Luminex) was used to measure 27 analytes in serum samples. Measurements were performed on matched samples from 144 healthy donors. To assess inter-plate variability, one arbitrarily selected serum sample was analyzed on each of the first ten plates as bridge sample. ResultsUsing the bridge sample, we showed minimal inter-plate variations in the measurement of most analytes. In measurement of cytokines from the 144 patients at two time points, we found that three cytokines (IL-2, IL-15 and GM-CSF) were undetectable and five analytes (RANTES, MCP-1, VEGF, MIP-1β and PDGF-BB) showed significant difference in concentrations at Day 0 compared to Day 7. ConclusionsThe current study demonstrated higher variations in cytokine levels among individuals than were observed for samples obtained one week apart from identical donors. These data suggest that a serum sample from each subject for use as a baseline measurement is a better control for clinical trials rather than sera from a paired cohort.     

The expression of interleukin-1 alpha, TNF and VEGF in corneal cells of patients with bullous keratopathy

Bullous keratopathy (BK) is a chronic corneal edema with or without subepithelial bullae as a result of a loss of the endothelial cells. 15 patients with BK after cataract surgery with intraocular lens implantation, due to Fuchs dystrophy (n = 3) or corneal endothelial trauma (n = 12) were included in the study. All patients were treated by amniotic membrane transplantation (AMT). Corneal epithelial cells in patients suffering from BK secreted 3.91 +/- 3.09 pg/mL of IL-1 alpha, 4446 +/- 16.8 pg/mL of TNF and 81.43 +/- 37.81 pg/mL of VEGF-I. Levels of all 3 investigated cytokines were significantly higher as compared to controls (p < 0.005). Amniotic membranes that were used to treat investigated patients contained 638.98 +/- 613.98 pg/mL of IL-1ra, 0.026 +/- 0.009 pg/mL of sTNF and 81.39 +/- 21.01 pg/mL of VEGF-R. Beneficial clinical effect of the AMT in treating BK could be explained by its natural production of pro-inflammatory cytokine antagonists such as IL-ra, sTNF antagonist and VEGF-R.     

Cytokine secretion depends on Galalpha(1,3)Gal expression in a pig-to-human whole blood model

Transplants from alpha1,3-galactosyltransferase (Gal) gene-knockout pigs to nonhuman primates are largely protected from hyperacute but not acute humoral xenograft rejection. The present study investigates the role of Gal in cytokine responses using a novel pig-to-human whole blood in vitro model, developed for species-specific analysis of porcine and human cytokines. Porcine (n = 7) and human (n = 27) cytokines were measured using ELISA or multiplex technology, respectively. Porcine aortic endothelial cells from control (Gal(+/+)) and Gal-deficient (Gal(-/-)) pigs were incubated with human lepirudin anticoagulated whole blood from healthy donors. E-selectin expression was measured by flow cytometry. The C3 inhibitor compstatin and a C5aR antagonist were used to study the role of complement. Cytokine species specificity was documented, enabling detection of 2 of 7 porcine cytokines and 13 of 27 human cytokines in one single sample. Gal(+/+) porcine aortic endothelial cells incubated with human whole blood showed a marked complement C5b-9 dependent up-regulation of E-selectin and secretion of porcine IL-6 and IL-8. In contrast, Gal(-/-) cells responded with E-selectin and cytokine expression which was so weak that the role of complement could not be determined. Human IL-6, IL-8, IFN-gamma, MIP-1alpha, MIP-1beta, eotaxin, and RANTES were detected in the Gal(+/+) system, but virtually no responses were seen in the Gal(-/-) system (p = 0.03). The increase in human cytokine release was largely complement dependent and, in contrast to the porcine response, mediated through C5a. Species-specific analysis of cytokine release revealed a marked, complement-dependent response when Gal(+/+) pig cells were incubated with human whole blood, compared with Gal(-/-) cells which induced virtually no cytokine release.     

Levels of some cytokines and antibodies to hepatitis C virus in patients with chronic hepatitis C

The comparison of the levels of some cytokines (tumor necrosis factor alpha (TNF-alpha), IL-1beta, IL-2, IL-4) in the blood serum of patients with chronic hepatitis C (CHC) having different antibody spectrum was carried out. In CHC patients increased levels of the serum cytokines IL-1beta, TNF-alpha under study in comparison with cytokine levels in donor sera was noted. In patients with detected antiNS5 and antiHCV IgM and antiNS5 HCV the level of IL-1beta was significantly higher than that in CHC patients without antibodies in sera. A change in the levels of proinflammatory and anti-inflammatory cytokines in the blood sera of CHC patients may be of significant diagnostic and prognostic importance.     

Serum from exercising humans suppresses t-cell cytokine production

Exercise affects t-cell cytokine production. Whether or not these effects are caused by circulating factors associated with physical activity (e.g., inflammatory mediators, acidosis) is unknown. To investigate this, we incubated sera (10%), obtained from 16 young-adults before (PRE) and after (END) 30-min of exercise, with commercially available Jurkat cells, a t-lymphocyte model, that, of course, had never been exposed to an exercise milieu. After 1 and 6h in culture, we measured in the supernatant four cytokines (each known to be altered by exercise and involved in disease pathophysiology): IL-2, TGF-beta1, TNF-alpha, and IL-1ra. Cell proliferation was assessed with proliferating nuclear cell antigen (PNCA). Statistical analysis consisted of a linear mixed model for repeated measurement. There was no effect of exercise on t-cell production of either TGF-beta1 or IL-1ra. In contrast, both IL-2 (p=0.025) and TNF-alpha (p=0.031) production was significantly suppressed in sera from the exercising participants. The suppression of these two cytokines occurred despite the fact that PNCA significantly increased (p=0.0004) in the END serum. In conclusion, exercise alters circulating factors that can, subsequently, influence t-cell cytokine production in vitro.     

Amniotic fluid levels of tumor necrosis factor-alpha and soluble tumor necrosis factor receptor 1 before and after the onset of labor in normal pregnancies.

Tumor necrosis factor-alpha (TNF-alpha) is present in human placental and uterine cells and promotes the regulation of trophoblast growth and invasion. Tumor necrosis factor receptor 1 (TNF-R1) is a receptor for TNF-alpha, and soluble TNF-R1 (sTNF-R1) is present in amniotic fluid after receptor shedding. We evaluated whether amniotic fluid TNF-alpha and sTNF-R1 levels during labor differed from those before the onset of labor in normal pregnancies. This study enrolled 34 Japanese women experiencing normal pregnancies with single fetuses who had no infection. Of these subjects, 17 went into labor and had subsequent term deliveries (the labor group), and the other 17 underwent cesarean section without labor (the nonlabor group). The average gestational age at entry was 38-39 weeks of gestation. Maternal ages and gestational ages did not differ significantly between the two groups. Amniotic fluid was collected and the TNF-alpha and sTNF-R1 levels were determined by the ELISA method. Each of these levels was compared between the two groups. There was a significant increase in amniotic fluid TNF-alpha levels in the labor group. However, amniotic fluid sTNF-R1 levels did not differ significantly between the two groups. Amniotic fluid TNF-alpha may promote the onset of labor at term and/or term labor contributing to subsequent delivery may induce the production and secretion of TNF-alpha into the amniotic cavity. There was no pregnancy-associated increase in receptor shedding or cell apoptosis at the onset of labor.     

In vivo intracellular cytokine production by leukocytes during haemodialysis

Several chronic inflammatory changes undergone during chronic haemodialysis are associated with increased pro-inflammatory cytokine production. Although generation of anaphylatoxins has been incriminated in the untoward effects of haemodialysis, it is still debated whether anaphylatoxins stimulate monocyte secretion of TNF-alpha and IL-1. We demonstrate that peripheral mononuclear cells isolated from healthy controls and cultured with complement-activated autologous serum or recombinant C5a induced high levels of IL-1, IL-1ra, IL-8 and MCP-1, low levels of TNFalpha and sTNFRII but no IL-10 and MIP-1alpha. Cytokine production by leukocytes was investigated by FACS analysis in six patients dialysed consecutively with three equivalent low permeability membranes known to activate the complement to different degrees: polysulfone (F6HPS), cellulose acetate (CA) and cuprophane (CP). Percentage of leukocytes expressing IL-1, IL-1ra, TNF-alpha and IL-8 is increased in patients dialysed with CP. Moreover, we show for the first time that haemodialysis is associated with the production of cytokines by circulating neutrophils. Predialysis plasma levels of MCP-1 and TNFRII did not increase during the dialysis session at the time when anaphylatoxin generation was highest. Dialysis with membranes that activate the complement to a high extent induce activation of leukocytes which may explain chronic complications associated with dialysing with CP.     

Developmental changes of free amino acids in bovine fetal fluids with gestational age and the interrelationships between the amino acid concentrations in the fluid compartments.

Thirty ninhydrin-positive compounds were determined in the sera, amniotic fluid, stomach content and allantoic fluid from 29 bovine fetuses of various gestational ages. Fetal serum was found to contain about 3-fold higher concentrations of free amino acids (FAA) than maternal serum, and allantoic fluid contained about 3-fold higher concentration of FAA than fetal serum. Decreasing concentrations of FAA were found in serum as a function of the crown-rump length for the amino acids taurine, aspartic acid, threonine, serine, ornithine and lysine. Decreasing concentrations of FAA in allantoic fluid were found for threonine, alanine and ornithine, whereas increasing concentrations were found for phosphoserine and methionine as a function of the crown-rump length. Correlations were found between the concentrations of most amino acids in amniotic fluid and stomach content, but fewer correlations were found between the other fluid compartments. The transport of amino acids between compartments is discussed.