Effect of insulin, prostaglandin E1 and uptake inhibitors on glucose transport in the perfused guinea-pig placenta

The effects of insulin, prostaglandin E1 (PGE1) and uptake inhibitors on unidirectional D-glucose influx at brush border (maternal) and basal (fetal) sides of the guinea-pig syncytotrophoblast were investigated in the intact, perfused guinea-pig placenta by rapid, paired-tracer dilution. Experiments were performed in either an in situ preparation artificially perfused through the umbilical vessels (intact maternal circulation) or in the fully isolated dually-perfused placenta in which both interfaces were studied simultaneously. Kinetic characterization of unidirectional D-glucose influx gave apparent Km values (mean +/- SEM) at maternal and fetal sides of 70 +/- 6 and 87 +/- 16 mM respectively; corresponding Vmax values were 53 +/- 3 and 82 +/- 6 mumol min-1g-1. At the fetal side (singly-perfused placenta) cytochalasin B (50 microM), ethylidene-D-glucose (100 mM) and PGE1 (1 microM) partially inhibited D-glucose uptake whereas cortisol (50 microM) and progesterone (100 microM) had no effect. Abolition of the sodium gradient across the fetal interface did not modulate the kinetics of influx. In the presence of 150 mu units ml-1 insulin (dually-perfused placenta), unidirectional uptake into the trophoblast and transplacental D-[3H]glucose transfer were unaltered. In contrast, prostaglandin E1 (1 microM) markedly reduced the Km and Vmax for D-glucose at both interfaces and the inhibitory effect was reflected in a reduction in specific transplacental D-glucose transfer. Further experiments showed that the isolated placenta releases prostaglandins (PGE; PGF2 alpha) into both circulations. Bilateral insulin perfusion did not affect either lactate release by the placenta or rapid metabolism of D-[14C]glucose to [3H]lactate (usually less than 10% effluent [14C]lactate in 5 min). An asymmetric degradation of exogenous insulin was observed in the dually-perfused placenta: uterine venous samples contained 24 +/- 7 microunits ml-1 immunoreactive insulin when compared to the arterial concentration (151 +/- 3 microU ml-1 perfusate) while no change was measureable in the fetal circulation within the same time period (152 +/- 5 microU ml-1). This asymmetry was confirmed in experiments employing [125I]insulin. These results demonstrate that glucose transport in the intact guinea-pig placenta occurs by a sodium-independent, cytochalasin B-inhibitable system which is insulin-insensitive. Prostaglandin E1 appeared to be a potent transport inhibitor which suggests that prostaglandins may be involved in the 'down' regulation of placental glucose transport in vivo.     

Evidence of saturable uptake mechanisms at maternal and fetal sides of the perfused human placenta by rapid paired-tracer dilution: studies with calcium and choline

Rapid uptake and efflux of 45Ca2+ and [3H]choline at the maternal and fetal interfaces of the syncytiotrophoblast in the dually-perfused human placenta was investigated by application of the single circulation paired-tracer dilution method (Yudilevich, Eaton, Short & Leichtweiss 1979). Cotyledons were perfused with Krebs-bicarbonate containing dextran (30 g/l; MW = 60-70,000) at 20 and 6 ml/min on maternal and fetal sides, respectively. The paired-tracer (test substrate and extracellular marker) technique consisted of an intra-arterial injection of a tracer bolus, followed by venous sampling over 5-6 min. There was a rapid (sec) uptake of 45Ca2+, followed by backflux (efflux into the ipsilateral circulation) which, over 5-6 min, was 59-100% on the fetal side. It was more variable but generally lower on the maternal interface. At 0.1 mM calcium, 45Ca2+ maximal uptake (Umax) was about 53% on the fetal side but on the maternal side it was variable and averaged 17%. At 2.4 mM calcium fetal side Umax was reduced to 40%. However, on the maternal side the effect was not consistent. Unidirectional influx (nmol/min per g) appeared to be not different on the two sides of the placenta. For [3H]choline (in choline-free perfusates) Umax was about 50% and 30% on fetal and maternal sides, respectively; tracer backflux was variable on the maternal side and averaged 50% on the fetal side. [3H]Choline uptake was highly inhibited by either 1.0 mM choline or the specific competitive inhibitor, hemicholinium-3 (0.1 mM). Specific transplacental transfer of 45Ca2+ (i.e. in excess of the extracellular marker) was not significant in either direction. For [3H]choline there was an apparent small excess (about 4%) preferential towards the fetal circulation. These findings in the human placenta are similar to those demonstrated previously in the guinea-pig placenta which suggested the existence of specific transport systems for choline and calcium on both sides of the syncytiotrophoblast.     

The effect of zinc levels in fetal circulation on zinc clearance across the in situ perfused guinea pig placenta

Although zinc is essential for normal fetal growth and development, little is known about factors that influence its transfer across the placenta. The in situ perfused guinea pig placenta model was used to study the influence of the zinc concentration of fetal circulation on maternofetal placental zinc transfer. A placenta of the anaesthetized sow was perfused (on the fetal side) with a physiological perfusate via the umbilical vessels, with the fetus excluded. The sow was infused intravenously with 65zinc as a tracer of placental Zn clearance, and with antipyrine as an indirect indicator of maternal placental blood flow. Maternal plasma and placental effluent samples collected at intervals were counted for 65zinc by gamma counter, and the absorbance of nitrosated antipyrine was measured at 350 nm. Varying the mean zinc concentration in the perfusate from 0.176 to 1.87 mg/L had no effect on relative zinc clearance calculated as zinc clearance/antipyrine clearance (mean +/- SEM; 0.085 +/- 0.010 vs. 0.114 +/- 0.018; n = 6; p greater than 0.05). The results suggest that short-term changes in fetal zinc status do not influence placental zinc transfer.     

Effects of histamine on vascular resistance and protein permeability in the isolated dually perfused guinea-pig placenta

The possibility that histamine can affect both the vascular resistance and permeability of the isolated dually perfused guinea-pig placenta has been investigated. Change from control to histamine (2.7 x 10(-4)M) perfusion of the fetal circulation elicited a significant (P less than 0.01, paired 't' test) maximum increase of 1.17 +/- 0.14 (SEM) kPa in fetal perfusion pressure 3 min later, representing a 33% rise. This vasoconstriction was completely blocked by the H1 antagonist diphenhydramine (10(-4)M) but not by the H2 receptor antagonist cimetidine (10(-4)M). In the same experiments the clearance (calculated as the ratio of fetal to maternal perfusate concentration times fetal flow-rate) of a macromolecular tracer, anionic horseradish peroxidase from the maternal to fetal circulation was significantly increased (P less than 0.05, paired 't' test) when steady state (15-20 min of perfusion) values were compared, from 5.9 +/- 1.7 (SEM) microliter min-1 placenta-1 to 12.9 +/- 3.5 (SEM) microliter min-1 placenta-1 (n = 20) for control and histamine respectively. By contrast the steady state clearance (calculated as before) of a smaller hydrophilic tracer, 51Cr-EDTA, was not significantly affected, being 587 +/- 59 (SEM) microliter min-1 placenta-1 in control and 587 +/- 55 (SEM) microliter min-1 placenta-1 (n = 20) with histamine perfusion. When histamine was perfused simultaneously with an H1 or H2 antagonist there was no change in anionic horseradish peroxidase clearance. Electron microscopy of placentas perfused with histamine failed to reveal any obvious alteration in morphology or anionic horseradish peroxidase localisation as compared to placenta perfused without histamine. This study thus demonstrates that histamine may cause changes in the macromolecular permeability of the placenta as well as vasoconstriction of the placental vasculature.     

Transplacental carbohydrate and sugar alcohol concentrations and their uptakes in ovine pregnancy

The concentrations of glucose, fructose, sorbitol, glycerol, and myo-inositol in sheep blood and tissues have been reported previously (1--5). However, the other polyols that are at low concentrations have not been investigated in pregnant sheep due to technical difficulties. By using HPLC and gas chromatography-mass spectrometry, seven polyols (myo-inositol, glycerol, erythritol, arabitol, sorbitol, ribitol, and mannitol) and three hexoses (mannose, glucose, and fructose) were identified and quantified in four blood vessels supplying and draining the placenta (maternal artery, uterine vein, fetal artery, and umbilical vein). Uterine and umbilical blood flows were measured, and uptakes of all the polyols and hexoses in both maternal and fetal circulations were calculated. There was a significant net placental release of sorbitol to both maternal and fetal circulations. Fructose was also taken up significantly by the uterine circulation. Maternal plasma mannose concentrations were higher than fetal concentrations, and there was a net umbilical uptake of mannose, characteristics that are similar to those of glucose. Myo-inositol and erythritol had relatively high concentrations in fetal plasma (697.8 plus minus 53 microM and 463.8 plus minus 27 microM, respectively). The ratios of fetal/maternal plasma arterial concentrations were very high for most polyols. The concentrations of myo-inositol, glycerol, and sorbitol were also high in sheep placental tissue (2489 plus minus 125 microM/kg wet tissue, 2119 plus minus 193 microM/kg wet tissue, and 3910 plus minus 369 microM/kg wet tissue), an indication that these polyols could be made within the placenta.     

Role of transferrin in iron transport between maternal and fetal circulations of a perfused lobule of human placenta

The transfer of iron between the maternal and fetal circulations of an isolated perfused lobule of term human placenta was investigated using 125I-labelled or 59Fe-labelled diferric transferrin. There was negligible transplacental transfer of intact transferrin whereas nearly 4 per cent of the added 59Fe was transferred into the fetal circulation after 2 h, where it became associated with fetal transferrin. Over 20 per cent of the added 59Fe radioactivity was sequestered within the placental tissue during this period, associated with transferrin, ferritin and other uncharacterized molecules. This suggests an important role for an intracellular pool in regulating transfer. The presence of 10 mM chloroquine in the maternal circulation substantially reduced tissue accumulation of 59Fe and totally inhibited transfer to the fetus. It is concluded that the initial stages of iron transfer to the fetus involve the internalization of maternal iron-saturated transferrin bound to membrane receptors by receptor-mediated endocytosis, which can be inhibited by the drug chloroquine. Subsequently, the transplacental transfer of iron to the fetus does not involve the concomitant movement of transferrin.     

Identification of luteinizing hormone releasing hormone-like immunoactivity in ovine cotyledons

Luteinizing hormone releasing hormone (LHRH)-like immunoactivity has been identified in cotyledonary extracts prepared from pregnant ewes. This activity displayed similar physico-chemical properties as synthetic LHRH, as determined by reverse-phase HPLC and size-exclusion HPLC. Under reverse-phase conditions, cotyledonary LHRH-like immunoactivity displayed a retention time (10.5 +/- 0.1 min) which was not significantly different from that of synthetic LHRH. When subjected to size-exclusion HPLC, cotyledonary LHRH-like immunoactivity eluted in fractions which corresponded to a molecular weight range of 1100-1200 Da, which was not significantly different from the elution profile observed for synthetic LHRH. The cotyledonary tissue content of LHRH-like immunoactivity averaged 94 +/- 24 pg/mg (n = 6). The results of this study demonstrate the presence of LHRH-like immunoactivity in ovine cotyledons. Although placental synthesis of LHRH-like immunoactive material has been demonstrated in other species, it remains to be established whether this activity, demonstrated in ovine placenta, is the consequence of de novo placental synthesis or represents uptake from the maternal (and/or fetal) circulation.     

Kinetic and metabolic studies of 15-methyl-prostaglandin F2α administered intra-amniotically for induction of abortion

The metabolism of tritium labeled 15-methyl-PGF_2α, administered intra-amniotically, was studied in seven cases of mid-trimester abortion. The disappearance of the compound from the amniotic sac was a very slow process. A metabolite, dinor-15-methyl-PGF_2α, was found in small amounts in the amniotic fluid and also in extracts of placenta and fetal liver, lung, and kidney. Plasma levels of 15-methyl-PGF_2α in the maternal circulation were determined.     

Lipopolysaccharide differently affects prostaglandin E2 levels in fetal and maternal compartments of perfused human term placenta

The aim of the present study was to examine the effect of lipopolysaccharide (LPS) on the levels of prostaglandin E(2) (PGE(2)) in the perfusates of the fetal and the maternal compartments of perfused human term placental tissue. Term placentas were perfused for 10h in the absence [control, (n=4)] and presence of LPS [LPS=1 microg/kg perfused placental tissue, (n=4)] in the maternal reservoir. Perfusate samples from the fetal and the maternal circulations were collected every 30 min and examined for PGE(2) levels by radio-immunoassay. PGE(2) levels in the fetal circulation were gradually increased reaching significant peak value of 479+/-159 pg/ml, as compared to PGE(2) levels in the maternal circulation (140+/-146 pg/ml) (p<0.05). After 10 hours of perfusion with control medium, PGE(2) levels in the maternal circulation (347+/-144 pg/ml) were significantly higher as compared to the fetal circulation (150+/-57 pg/ml) (p<0.05). In presence of LPS, PGE(2) levels in the fetal circulation increased reaching a peak value of 1028+/-663 pg/ml after 240 min of perfusion. The levels of PGE(2) in the control group after 240 min of perfusion were significantly lower (156+/-77 pg/ml) (p<0.05). No significant differences were detected in the levels of PGE(2) in the perfusate of the maternal compartment in presence of LPS, as compared to control. Our results suggest that the placenta may play an important role in maintaining high levels of PGE(2) in the fetal circulation and low PGE(2) levels in the maternal circulation during normal pregnancy. Moreover, placental PGE(2) release into the fetal and the maternal circulations may be differently affected in presence of intra-uterine infection/inflammation.     

Urea and amino acid transport by an isolated human placenta]

A method of bilateral perfusion of the isolated human placenta was used to study the urea transport from the fetal placental stream into the maternal one, and of amino acid transport in the opposite direction. Experiments demonstrated that the method provided a sufficiently full perfusion of the intervillous space and offered possibilities for studying the placental transport. With equal amino nitrogen concentration in both circulations, its content in the fetal stream increased during the experiment. This elevation was more expressed when amino acid was added to the maternal circulation. The idea of amino acid "secretion" by the trophoblast cell elements into the fetal circulation was confirmed by the above experiments.     

The metabolism of prostaglandin E2 in perinatal rabbit lungs

The inactivation of prostaglandin E₂ (PGE₂) was studied in isolated perfused lungs of fetal and neonatal rabbits. 200 nmol of ¹⁴C-PGE₂ was infused into the pulmonary circulation and the metabolites of PGE₂ were analysed from the nonrecirculating perfusion effluent. The amount of the main metabolite, 13,14-dihydro-15-keto-PGE₂, increased significantly between the 28th and 30th day of fetal life, remained relatively constant at the time of birth and increased again between 1st and 7th postnatal day. In contrast the amount of 15-keto-PGE₂ remained relatively stable during the studied period. The activity of NAD⁺-dependent 15-hydroxyprostaglandin dehydrogenase (15-OH-PGDH) was determined from the 100.000 g supernatant fraction of fetal, neonatal and maternal rabbit lungs using ¹⁴C-PGE₂ (20 μM) as the substrate. In the lungs of late fetal rabbits the activity of 15-OH-PGDH was significantly higher compared to the early postnatal period. Maternal rabbit lungs possessed, however, very high activities compared to the studied perinatal lungs. The results show, that the activity of the pulmonary 15-OH-PGDH is high already during the late fetal period. The inactivation of PGE₂ in isolated perfused lungs seems, however, to increase during the last prenatal days. Thus it seems possible that the uptake mechanism could be the rate limiting step in the metabolism of PGE₂ in rabbit lungs during the perinatal period.     

Effects of altering umbilical flow and umbilical free fatty acid concentration on transfer of free fatty acids across the rabbit placenta

The transfer of free fatty acids across the placenta perfused in situ was studied in anaesthetized rabbits in late gestation. In the first series of experiments, umbilical flow rate was varied between 0.6 and 4.0 ml/min in nine rabbits. Although increasing umbilical flow rate significantly decreased the free fatty acid concentration in the umbilical venous effluent (P = 0.0001), placental clearance of free fatty acids from the maternal circulation was not significantly changed by alterations in umbilical flow rate. In the second series of experiments, the materno-fetal free fatty acid concentration gradient was varied between + 1.58 mmol/l and -2.81 mmol/l in eight rabbits. There was a significant relationship between increasing materno-fetal gradient and increasing transfer of free fatty acids across the placenta (P less than 0.001). Moreover, net transfer of free fatty acids into the umbilical circulation was observed even with zero concentration gradient. Net transfer of free fatty acids from fetus to mother occurred when umbilical arterial free fatty acid concentration exceeded maternal arterial concentration by 1.3 mmol/l.     

3'-azido-3'-deoxythymidine (AZT) transplacental perfusion kinetics and DNA incorporation in normal human placentas perfused with AZT.

Vertical transmission of the human immunodeficiency virus 1 (HIV-1) is reduced from approximately 25% to approximately 7% as a result of 3'-azido-3'-deoxythymidine (AZT) therapy given during pregnancy; however, the consequences of transplacental AZT exposure to the fetus remain unknown. To address the extent and kinetics of AZT transfer across the human placenta, perfusion studies have been performed with fresh uninfected human placentas perfused with 0.5, 1. 0 and 5.0 mg AZT/ml for 2 h using a dual recirculating single cotyledon perfusion apparatus [T.I. Ala-Kokko, P. Pienimaki, R. Herva, A.I. Hollmen, O. Pelkonen, K. V?h?kangas, Transfer of lidocaine and bupivacaine across the isolated perfused human placenta, Pharmacol. Toxicol. 77 (1995) 142-148]. For two placentas, samples of perfusion effluent were taken every 15 min from the maternal and fetal sides of the apparatus and AZT levels were determined by AZT radioimmunoassay (RIA). At the end of the perfusion, AZT-DNA incorporation into placental DNA was determined by AZT-RIA. The concentration of AZT in the fetal perfusate increased with time, along with a concomitant slow decrease in the concentration of AZT in the maternal perfusates. For three different placentas, at 2 h after the start of perfusion, AZT-DNA incorporation values (molecules of AZT/10(6) nucleotides) were 11.8 for the 0.5 mg AZT/ml perfusate, 13.7 for the 1.0 mg AZT/ml perfusion, and 42.0 for the 5 mg AZT/ml perfusion. An additional placenta perfused with 1 mg AZT/ml did not have detectable values of AZT incorporated into DNA (data not shown). The data show that AZT crosses the human placenta and becomes rapidly incorporated into DNA of placental tissue in a dose-dependent fashion, suggesting that even short exposures to this drug might induce fetal genotoxicity and might also inhibit maternal-fetal viral transmission.     

Placental essential fatty acid transport and prostaglandin synthesis

The studies reported here demonstrate two important aspects of placenta EFA transport and metabolism. (1) A mechanism exists within the placenta for the selective incorporation of 20:4 omega 6 into phosphoglycerides and the export of those phosphoglycerides to the fetal circulation. This mechanism allows the selective sequestering of 20:4 omega 6 in the fetoplacental unit and may provide the fetus with important performed structural membrane components. (2) Placental PG synthesis is directed mostly to the maternal circulation and stimulated placental PG synthesis is directed totally to the maternal circulation. This mechanism may protect the fetus from fluctuations in maternal and placental PG synthesis and may direct stimulated placental PG synthesis to a target organ, the myometrium. The perfused human placental model provides a valuable method for the study of a variety of biochemical phenomena in a whole human organ and its use may further elucidate the role of this tissue in the maintenance of pregnancy, the transport of EFA to the developing fetus and the involvement of placental PG synthesis in fetal development and parturition.     

Evaluation of bidirectional transfer of plasma DNA through placenta

To clarify the origin of cell-free fetal DNA in maternal plasma, we analyzed bidirectional transfer of plasma DNA between fetus and mother. We analyzed maternal and fetal plasma DNA obtained from 15 pregnant women at the time of Cesarean section. The subjects were five patients with preeclampsia and 10 gestational-age-matched normal controls. DNA was extracted from 1.5-ml plasma samples and the cellular fraction of maternal and umbilical blood. Seven polymorphic marker genes were analyzed. The relative concentration of fetal DNA in maternal plasma and maternal DNA in cord blood were evaluated. The relative concentration of maternal DNA in fetal circulation (median, 0.9%; range, 0.2–8.4%) was significantly lower than that of fetal DNA in maternal blood (14.3%, 2.3–64%), with P=0.007. The relative concentration of maternal DNA in fetal blood was not affected by preeclampsia. These findings indicate that cell-free DNA is unequally transferred through the placenta. The structural characteristics of the placenta suggest that the majority of cell-free fetal DNA in maternal plasma is derived from villous trophoblasts.     

Uptake,transfer and metabolism of prostaglandin E2 in the isolated perfused human placental cotyledon

(³H) PGE₂ uptake and transfer in the isolated perfused human placental cotyledon was assessed by a ingle pass paired isotope dilution technique utilising (¹⁴C) sucrose as an extracellular marker. Metabolism of (³H) PGE₂ was measured by analysing maternal and fetal effluents from perfused human placental cotyledons after bolus injection of (³H) PGE₂ into ither the maternal or fetal sides. Maximal uptake of (³H) PGE₂ was greater on the maternal (81 +/- 8%) than the fetal sides (42 +/- 12%) and showed saturation with increasing concentrations of PGE₂ only on the fetal side with an apparent Km of 12 +/- 4.9 nmol/l and v_max of 1.5 +/- 0.2 pmol/min/g. Total recoveries of (³H) PGE₂ were 84.6 +/- 11.8 % and 32.6 +/- 6.3 % of the injected dose after injection on the fetal and maternal sides respectively.Transferof (³H) PGE₂ was the same in both directions being 6.4 +/- 1.2 % of the injected dose in the fetal-maternal direction and 5.8 +/- 2.7 % of the injected dose in the maternal-fetal direction. Metabolism was greater on the maternal side (35% of injected (³H) PGE₂) thanthe fetalside(18% of injected (³H) PGE₂) and was principally to the 13,14-dihydro-15-keto-PGE₂ metabolite. Metabolism of (³H) PGE₂ after passage across the placenta was the same in both directions and was of the order of approximately 60%.     

Fetal-maternal transfer of [H3]-6 beta-hydroxycortisol in the pregnant ewe

Distribution and fetomaternal transfer of 6 beta-hydroxycortisol (6 beta-OHF) was studied using serial sampling following injection of tritium labelled 6 beta-OHF into various fluid compartments in the chronically cannulated unaesthesized pregnant ewe. There was a rapid transfer of 6 beta-OHF from the fetal circulation into amniotic fluid and maternal blood. In contrast, the maternal----fetal transfer of this steroid metabolite was considerably less. The sequence of appearance of 6 beta-OHF in fetal blood and amniotic fluid following injection into maternal blood suggests that this steroid is first transferred across the placenta to fetal blood before gaining entry into the amniotic fluid space. The half-lives of 6 beta-OHF after initial equilibration in maternal plasma, fetal plasma and amniotic fluid were 2.0 h, 5.1 h and 8.9 h respectively. The amniotic sac appears to contain a relatively static pool of 6 beta-OHF and may act as a "trap" for 6 beta-OHF in the ovine conceptus.     

The effect of carbacyclin, a prostaglandin analogue, on adenylate cyclase activity in platelet membranes

The effect of carbacyclin, a chemically stable analogue of prostacyclin, on the activity of adenylate cyclase in platelet membranes was measured, and compared with the effect of PGE1. When GTP was added in concentrations up to 10 microM the activation of adenylate cyclase by carbacyclin was increased, whereas higher concentrations of GTP were inhibitory. The addition of a non-hydrolysable analogue of GDP, guanosine 5'-[beta-thio]diphosphate (GDP[beta S] ) resulted in a dose-dependent inhibition of adenylate cyclase activation by carbacyclin; this inhibition was relieved by adding increased amounts of GTP.     

On the dual localization of lipoprotein lipase in rat heart. Studies with a modified perfusion technique

Rat hearts were perfused $\text{in vitro}$ using a modified $\text{Langendorff}$ technique, allowing the separate collection of coronary- and interstitial effluents. When heparin was added to the perfusion medium lipoprotein lipase was found in the coronary, as well as in the interstitial effluents. The relative amounts of lipase activity in both effluents varied with the feeding conditions of the animals, being high in the coronary effluent during fasting and high in the interstitial effluent during feeding. When glucagon (2.10^?7 M) was included in the perfusion medium, no differences between fasted and fed animals were obtained. The apparent K_m of the interstitial lipase was lower than that of the lipase found in the coronary effluent. The results are discussed in the light of the localization of lipoprotein lipase in rat hearts $\text{in situ}$.     

Eicosanoid production and transfer in the placenta of the diabetic pregnancy

The metabolism of arachidonic acid (AA) and the transfer of its metabolites was determined in in vitro perfused placental tissue from normal pregnancies and those complicated by maternal insulin-dependent diabetes mellitus (IDDM). 14C-labelled AA was recirculated in the fetal circulation for 60 min while 3H-AA was recirculated in the maternal circulation. Placental effluent was subjected to high performance liquid chromatography (HPLC) and analysis of dual-label scintillation counts. Placentae from IDDM pregnancies converted 3-6 times more radiolabelled AA to eicosanoids than did normal placentae. In addition, the transfer of eicosanoids into the opposing circulation was doubled in placentae from IDDM pregnancies compared to normal placentae. The predominant direction of eicosanoid transfer in both groups of placentae was in the fetal-to-maternal direction. The relative amounts of eicosanoids produced was also altered in placentae from IDDM pregnancies. Increased amounts of thromboxane (Tx) B2 and hydroxyeicosatetraenoic acids (HETEs) were present in both circulations of placentae from IDDM pregnancies. Levels of 6-keto prostaglandin F1a (6KPGF1a) were significantly reduced in both circulations in placentae from IDDM pregnancies. Thus, the ratio of TxA2 to PGI2 and the ratio of HETEs to PGI2 were both significantly increased in placentae from IDDM pregnancies. These results suggest an imbalance in eicosanoid production which may be relevant to abnormal placental structure and function in IDDM pregnancies.