Occurrence of phosphodiesterase IV in the developing human brain, liver and placenta

Ontogenic profile of some antioxidants and lipid peroxidation in human placental and fetal tissues

Reactive oxygen species (ROS) pose a serious threat to maternal and fetal health during pregnancy. However, there is little information on the oxidative damage caused by ROS and its protection during prenatal life. The present study highlights the status of various antioxidants in human placental and fetal tissues at different phases of gestation. The activity profile of scavenging enzymes, superoxide dismutase, catalase, glutathione peroxidase and glutathione reductase as well as the concentrations of non-enzymatic antioxidants, ascorbic acid, alpha-tocopherol, bilirubin and glutathione have been determined in human placental whole homogenate, placental brush border membrane and fetal liver over gestational periods ranging from 6 weeks of pregnancy till birth. The ontogenic profile of lipid peroxidation, a marker of oxidative damage has also been investigated in the feto-placental system. Catalase, superoxide dismutase and glutathione reductase activities increased significantly, but glutathione peroxidase activity remained almost the same throughout development. Except alpha-tocopherol and bilirubin, the concentrations of other non-enzymic scavengers followed a significant increasing trend with advancement of pregnancy. Results indicate that there is gradual suppression of lipoperoxide formation with the progress of gestation to protect the fetus against oxygen toxicity.

Antioxidant status and lipid peroxidation in human feto-placental unit

The human feto-placental unit being in the environment of the materno-fetal circulation is very much susceptible to the danger of reactive oxygen species-induced oxidative damage. The present study reports the status of various antioxidants in the feto-placental system at birth. The activities of superoxide dismutase, catalase, glutathione peroxidase and glutathione reductase as well as concentrations of non-enzymic antioxidants viz, ascorbic acid, alpha-tocopherol, bilirubin and glutathione have been determined in term placental brush border membrane (BBM) and umbilical cord (UC) blood. The extent of lipid peroxidation in developing and term BBM and UC blood has been studied by estimation of malondialdehyde and conjugated dienes, both being the end products of lipid peroxidation. The results indicate the presence of a protective mechanism against oxygen toxicity in the feto-placental system at the time of parturition.

Changes in lipid composition and fluidity of human placental basal membrane and modulation of bilayer protein functions with progress of gestation

Human placental syncytiotrophoblast basal membrane plays an important role in transfer of nutrients from the mother to the growing fetus all throughout gestation. The membrane lipid composition together with the bilayer fluidity is found to be the major index in modulation of these transport processes. In the present study, the effects of changing lipid composition on the placental basal membrane fluidity and the modulating influence of the latter on membrane enzyme and transport functions with progress of gestation,were investigated. Steady-state fluorescence analysis using 1,6-diphenyl- 1,3,5 hexatriene as the probe, indicated a decrease in fluorescence anisotropy of both labeled native membrane vesicles and liposomes prepared from lipids extracted from the basal membrane vesicles, signifying increased bilayer fluidity with progress of gestation. This in turn, was successfully correlated to the lowering of cholesterol content and enhanced phospholipid concentration with a steady decrease in cholesterol/phospholipid ratio during placental development. Enhanced Na+-K+-ATPase activity and steady-state glucose uptake across basal membrane with gestational progress suggested modulation of membrane protein functions by the fluidity, which was further corroborated by the increased bilayer fluidity and enzyme activity in benzyl alcohol treated basal membrane in each gestational age group.

Increase in fluidity of human placental syncytiotrophoblastic brush-border membrane with advancement of gestational age: a fluorescence polarization study

The syncytiotrophoblastic brush-border membrane (BBM) of human placenta plays a vital role in the exchange of metabolites between mother and developing fetus. The fluidity of this membrane renders its selective permeable character. To meet the changing needs of the growing fetus with the progress of gestational age changes in the composition and properties of BBM occur. In the present study, decrease in cholesterol/phospholipid ratio of BBM indicated an increase in fluidity with advancement of gestational age. Measurement of the steady state fluorescence anisotropy of labeled liposomes prepared from lipid extract of BBM as well as that of labeled BBM vesicles prepared from native BBM shows decrease in restriction of the bound dye molecule with increased gestational age. Decrease in transition temperature of BBM and enhanced glucose transport through it have been observed with advancement of pregnancy.

Characterization of cardiac fatty-acid-binding protein from human placenta. Comparison with placenta hepatic types

When a 105,000 x g supernatant of human placenta was incubated with [1-14C]oleate and subjected to Sephadex G-75 gel filtration and HPLC, two fatty-acid-binding protein (FABP) peaks were obtained. One of these, when further purified by carboxymethyl-cellulose, gave one 15.3-kDa FABP with pI5.3. The other, when chromatographed on DEAE cellulose, separated into two 14.2-kDa FABP with pI6.9 and 5.4. Purity of the proteins was checked by SDS/PAGE. Molecular mass, pI, immunochemical properties and amino acid compositions all indicated that 15.3-kDa FABP was of the cardiac type, whereas both 14.2-kDa FABP were of the hepatic type. Cardiac FABP did not cross-react with hepatic proteins. When tested for the acceptor/donor properties of these FABP, hepatic types were found to be better candidates than cardiac in uptaking fatty acids from liposomes. Cardiac FABP, on the other hand, acted in a more efficient way as a donor, indicating a distinct role of these proteins in human placenta, which furnishes a multiorgan system for the developing fetus.

Human fetal liver fatty acid binding proteins. Role on glucose-6-phosphate dehydrogenase activity

Fatty acid binding proteins (FABPs) may play an important role in the transport and metabolism of fatty acids during human embryogenesis. Three fractions of FABP, namely, DE-I, DE-II and DE-III, having Mr 14,200 Da each and pI values 7.8, 6.9 and 5.4, respectively, have been detected in human fetal liver. These proteins were purified by heat and butanol precipitation of fetal liver supernatant as well as by gel filtration and ion-exchange chromatography. Fetal liver FABPs are immunochemically identical to each other. Concentrations of DE-I, DE-II and DE-III increase gradually from early gestation to term. DE-I is almost lipid-free, DE-II binds long-chain fatty acids nonspecifically and DE-III transports mainly arachidonic acid. DE-II and DE-III protect glucose-6-phosphate dehydrogenase, which furnishes NADPH for fatty acid synthesis, from the feed-back inhibition exerted by added palmitoyl-CoA and oleate. In the absence of exogenous inhibitors, this enzyme is stimulated by FABPs. DE-I has no effect on such inhibition. Thus, FABPs play a regulatory role in critical aspects of cellular physiology during human embryogenesis.

Purification and characterization of fatty acid-binding protein from human placenta

Purification of a cytosolic fatty acid-binding protein (FABP) from developing human placenta has been achieved, and its role in modulating the inhibition of human placental glucose-6-phosphate dehydrogenase (G6PD) by palmitoyl-CoA (PAL-CoA) has been studied. FABP was resolved into three peaks, viz. DE-I, DE-II and DE-III, by DEAE cellulose chromatography. DE-I was almost lipid-free. Presence of endogenous fatty acids in DE-II and DE-III was detected by thin layer chromatography (TLC). Fatty acids were the only detectable lipid component in these fractions. Gas liquid chromatography (GLC) analysis revealed that DE-II binds long chain saturated and unsaturated fatty acids nonspecifically, whereas DE-III is mainly an arachidonic acid carrier. Each of these fractions, viz. DE-I, DE-II and DE-III, has a molecular weight of 14,200 Daltons. Ouchterlony double immunodiffusion studies have confirmed the immunochemical identity of these three fractions of placental FABP. Separation in ion exchanger may be due to their different isoelectric points and varied types of binding affinities. Human placental G6PD was inhibited 50% by 0.03 mM PAL-CoA. The DE-II fraction of FABP enhanced the activity of G6PD in the absence of added PAL-CoA and protected against PAL-CoA inhibition of the enzyme. Such a modulating effect of FABP in this inhibition is attributable to binding of long chain acyl-CoA rather than to a direct effect of FABP on the enzyme itself.

A comparative study of human placental and fetal liver catalase during development

The activity and a few properties of catalase have been compared in the developing human placenta and fetal liver. The presence of the enzyme in both the tissues is discernible as early as in the 6th wk of gestation and the activity increases gradually with the advancement of pregnancy. Maximum enzyme activity in both placenta and fetal liver is found to be associated with the soluble supernatant fraction obtained by centrifuging the tissue homogenates at 105000 X g. Kinetic studies reveal the enzymatic decomposition of H2O2 to follow first-order kinetics at lower substrate concentrations, and then to deviate from the original linearity, demonstrating mixed-order kinetics. Thermostability of placental catalase increases with prenatal development, while the enzyme from fetal liver remains moderately heat-stable throughout the gestation. Treatment of the homogenates with Triton X-100 is found to be most effective in increasing catalase activity in each of these tissues.

Ontogeny of polyamines in relation to nucleic acids in brain and spinal cord of the developing human fetus

The polyamines, spermine and spermidine, and the diamine, putrescine, were estimated in relation to the distribution of RNA and DNA in cerebral cortex, cerebellum and spinal cord of the human CNS during prenatal development. Polyamines were found to be maximally located in the spinal cord, minimum being in cerebellum. Relation between polyamines and nucleic acids was region specific.