On the Phagocytosis of Iron‐dextran by the Human Plasmoditrophoblast

Muir, A L

doi:10.1111/j.1471-0528.1966.tb06121.x

Cited by 5 publications

(2 citation statements)

References 13 publications

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“…Phagocytosis and pinocytosis are slow mechanisms of transport that have been described in the intestinal mucosa, [66) in the basic trophoblast [67][68][69] and in the early stages of implantation in humansJ70,71J However, it is likely that this system is too slow to have importance in the transfer of drugs and, therefore, has received little attention, Indeed, other investigators [55) have observed small breaks in the placental membrane, This is apparently the mechanism by which erythrocytes cross the placenta, but it is not known whether drugs also transfer in this manner, The electrochemical gradient across the placenta is 20m V,l72) Such a gradient may, at least in part, be due to the difference in pH (0,1 to 0,15 units) between the fetal and maternal blood, [14 [ Weak bases tend to be more dissociated in the fetal than in maternal blood, Thus, the electrochemical gradient may be of importance for the ionisable drugs having a pK near the pH of blood,…”

Section: Facilitated and Active Transportmentioning

confidence: 99%

Placental Transfer of Drugs Administered to the Mother

Pacifici

Nottoli

1995

Clinical Pharmacokinetics

282

119

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Drugs administered to mothers have the potential to cross the placenta and reach the fetus. Under particular circumstances, the comparison of the drug concentration in the maternal and fetal plasma may give an idea of the exposure of the fetus to the maternally administered drugs. In this review drugs are classified according to their type of transfer across the placenta. Several drugs rapidly cross the placenta and pharmacologically significant concentrations equilibrate in maternal and fetal plasma. Their transfer is termed 'complete'. Other drugs cross the placenta incompletely, and their concentrations are lower in the fetal than in maternal plasma. The majority of drugs fit into 1 of these 2 groups. A limited number of drugs reach greater concentrations in fetal than maternal plasma. It is said that these drugs have an 'exceeding' transfer. The impression prevails that suxamethonium chloride (succinylcholine chloride) and doxorubicin do not cross the placenta. However, a careful analysis of the literature suggests that this impression is wrong and that all drugs cross the placenta, although the extent transfer varies considerably. The following parameters were considered as possible factors determining the extent of placental transfer: (i) the molecular weight of the drug; (ii) the pKa (pH at which the drug is 50% ionised); and (iii) the extent of drug binding to the plasma protein. Drugs with molecular weights greater than 500D have an incomplete transfer across the human placenta. Strongly dissociated acid drug molecules should have an incomplete transfer, but this does not seem to be an absolute rule. For example, ampicillin and methicillin transfer completely and they are strongly dissociated at physiological pH. The extent of drug binding to plasma protein does not influence the type of drug transfer across the human placenta.

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Section: Facilitated and Active Transportmentioning

confidence: 99%

Placental Transfer of Drugs Administered to the Mother

Pacifici

Nottoli

1995

Clinical Pharmacokinetics

282

119

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“…One patient was delivered the same day and several others went into labour within 10 days, but in most cases the infusion was given more than three weeks before delivery.…”

Section: Resultsmentioning

confidence: 99%

Effect of total dose infusion of iron dextran on the storage iron content of the human placenta.

Bauminger¹,

Walters²,

Whicher³

et al. 1982

J Clin Pathol

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SUMMARY In a series of pregnant women with iron deficiency anaemia treated by a total dose infusion of iron dextran, the non-haem iron content of the placenta at term was studied histochemically and by chemical analysis. Within a few days of the infusion the Prussian blue reaction on the placenta was very strong, but was negative by ten days after the infusion. Chemical analysis showed that both the water-insoluble fraction (haemosiderin) and the water-soluble fraction (ferritin) of the non-haem iron were increased soon after the infusion, but three weeks after the infusion they were almost the same as in untreated controls. Pinocytosis of iron dextran by the trophoblast and increased transport of transferrin-bound iron to the placenta are considered as possible causes for this large uptake of iron by the placenta.The histochemical examination of a placenta obtained from a stillbirth which occurred three days after the mother had received a total dose infusion of iron dextran, at 32 wk gestation, revealed very large amounts of haemosiderin in the trophoblast. This is in contrast to the findings of Pathak et all who concluded from a study of a large series of irondeficient patients treated with total dose infusion of iron dextran that there was no resulting increase of stainable iron in the placenta. There are two features of the stillborn baby which may have contributed to the accumulation of an unusually large amount of haemosiderin in the placenta. First, the foetus was macerated, so that transfer of iron to the foetus must have ceased soon after the infusion, and secondly, the gestational age of the placenta was only 32 wk when it was examined. Further studies were therefore made to assess in more detail the effect on placental iron of infusions of iron dextran given at different stages of pregnancy. In addition to histochemical examination of the placenta, the two forms of storage iron, haemosiderin and ferritin, were estimated respectively as the water-insoluble and water-soluble fractions of the non-haem iron. Non-haem iron For the estimation of non-haem iron the amnion and chorion were removed from the rest of the placenta which was then blotted dry between layers of filter paper and the whole of it was homogenised. The homogenate was again blotted dry to remove released blood and a weighed aliquot was shaken for 15 min with water, which had been deionised and then glass-distilled, to extract the water-soluble iron. After centrifugation the supernatant was removed for estimation of its iron content and the deposit was extracted once more with water.

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Electron microscopic observations on fibrinoid and histiotroph in the junctional zone and villi of the human placenta

1970

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The surfacr of syncytiotrophoblast covering primary villi in the early human placenta may be smooth, lacy, exhibit a brush border with highly developed straight or branched microvilli, or display projections. These projections may have microvilli and they may contain granules, vacuoles and mitochondria. By contrast, syncytium of the basal or junctional zone has longer and straighter microvilli and numerous projections often extend as long, recurving streamers which penetrate into and engulf the cytolyzed detritus of decidual cells. These streamers contain granules, vacuoles and microvilli. Granular detritus is evident between the microvilli, adherent to their surfaces and in the bays and superficial vacuoles at or just beneath the surface plasma membrane, indicating that phagocytosis and pinocytosis occur in the basal trophoblast.In occasional areas in the intervillous space and regularly in the basal junctional zone, clots composed of fibrin fibrils occur. Associated with them are amorphous masses of similar electron density. These represent different degrees of maternal blood clotting, possibly associated with clotting agents released after damage to fetal cells.Fibrin clots and associated leucocytes adhere to the surface of the syncytium, penetrate into it and between the Langhans' cells, occasionally replacing the trophoblastic layers entirely. In such areas, transudates of maternal blood have direct access to the connective tissues of the fetal villus.

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On the Phagocytosis of Iron‐dextran by the Human Plasmoditrophoblast

Cited by 5 publications

References 13 publications

Placental Transfer of Drugs Administered to the Mother

Placental Transfer of Drugs Administered to the Mother

Effect of total dose infusion of iron dextran on the storage iron content of the human placenta.

Electron microscopic observations on fibrinoid and histiotroph in the junctional zone and villi of the human placenta

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