Potential differences between mother and foetus at different gestational ages in the rat, rabbit and guinea‐pig

Mellor, D. J.

doi:10.1113/jphysiol.1969.sp008919

Cited by 38 publications

(26 citation statements)

References 10 publications

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“…ranged from -9 to -27 mV, with an average value of -17-9 + 141 mV (n = 19, perfusion with calf serum), which J. 9TULC AND J. SVIHOVEC is in good agreement with the value of -18mV (Mellor, 1969), or -21-4mV (Stulc et al 1972) recorded between mother and living foetus in the guinea-pig.…”

supporting

confidence: 71%

“…) between the maternal and foetal sides of the placenta has been recorded in a number of species. The potential of the foetus with respect to the mother was from -25 to -133 mV in the goat (Meschia, Wolkoff & Barron, 1958), from -25 to -45 mV (Widdas, 1961) or about -51 mV (Mellor, 1970) in the sheep, about -18 mV (Mellor, 1969) or -21 mV (8tulc, Rietveld, Soeteman & Versprille, 1972) in the guinea-pig, 0 mV in the rabbit, + 15 mV in the rat (Mellor, 1969), and 0 mV in humans at term (Mellor, Cockburn, Lees & Blagden, 1969). The site of origin of the p.d.…”

Section: Introductionmentioning

confidence: 99%

“…In the guinea-pig the p.d. between mother and living foetus was about -20 mV (Mellor, 1969;9tulc et al 1972). The values below -10 mV were very rare and usually due to faulty positioning of the foetal agar bridge in the vitelline vessels (J.…”

mentioning

confidence: 99%

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Effects of potassium cyanide, strophanthin or sodium‐free perfusion fluid on the electrical potential difference across the guinea‐pig placenta perfused in situ

S̆tulc¹,

Švihovec²

1973

The Journal of Physiology

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confidence: 71%

Section: Introductionmentioning

confidence: 99%

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Effects of potassium cyanide, strophanthin or sodium‐free perfusion fluid on the electrical potential difference across the guinea‐pig placenta perfused in situ

S̆tulc¹,

Švihovec²

1973

The Journal of Physiology

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“…Studies on transplacental potential differences in various mammals showed the presence of a positive charge on the fetal side of the placenta in the rat (12). The implication of this finding is that all of the reported fetal-maternal concentration relationships would require the presence of active transfer of potassium towards the fetus.…”

mentioning

confidence: 67%

“…Measurements of electrical potential were carried out according to the well described methodology of Mellor (12). The fiber end of one calomel electrode was placed in the maternal peritoneal fluid.…”

Section: Methodsmentioning

confidence: 99%

Fetomaternal Potassium Relations in the Fetal Rat on the Twentieth Day of Gestation

Fantel

1975

Pediatr Res

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Extract when pentobarbital was employed as the anesthetic agent (I I). It isTime-corrected measurements of transplacental and transamniotic potentials were made in the fetal rat on the 20th day of gestation. These averaged 14.3 mV and 18.4 mV, respectively. The measured maternal potassium concentration in plasma of 4.8 mEq/liter and these potential measurements were used in the Nernst equation to predict the fetal concentrations in plasma. The concentration in amniotic fluid was predicted, using the potentials and either the fetal or maternal plasma concentration. The predicted concentrations in fetal plasma and amniotic fluid were 2.8 and 2.5 mEq/liter, respectively. The sampling time-corrected potassium concentration in fetal plasma was 2.9 mEq/liter and the mean in amniotic fluid was 4.6 mEq/liter. The observed concentration in amniotic fluid is significantly higher than the predicted level. SpeculationPotassium is passively distributed between maternal and fetal plasma according to electrochemical gradients. By contrast, there is active transfer of this ion into the amniotic fluid, probably from the fetal plasma across the kidney.The rapid increase of cell mass in the developing conceptus would be expected to create a critical demand for potassium in the fetus as a result of high intracellular concentrations of this solute. Because of the importance of the extracellular fluids as the immediate source of the solutes available to cells, there have been many studies of potassium concentrations in the plasma of maternal and fetal animals carried out during the past 20 years. Many of the studies have been performed on the rat where there has been considerable disagreement on the appropriate fetal values. Whereas maternal concentrations have ranged from 4.6 to 5.4 mEq/liter (averaging 4.9 mEq/liter), fetal values in these same studies have ranged from 4.3 to 9.0 mEq/liter (see Table I). Since almost all of the studies have been performed on pregnant rats at similar stages of gestation, and on the same or related strains, it is likely that methodologic differences between studies have been responsible for the differences.It has been demonstrated that ion concentrations in fctal plasma are relatively dependent upon the state of fetal oxygenation (3, 13). Episodes of fetal hypoxia lead to the extracellular accumulation of molecules normally found in high concentration within cells. This was shown to rapidly elevate the total osmotic pressure of fetal plasma as well as to increase its potassium concentration. I n the rat, it has been shown that events which are likely to induce fetal hypoxia, such as killing of the dam. ligation of uterine arteries, or umbilical cord section, lead to significant increases in the potassium concentrations found (10). Potassium concentrations in the plasma of the fetal rat will increase as a function of the time elapsing between removal of fetuses from the uterus and plasma sampling (2). It has also been demonstrated that maternal ether anesthesia resulted in higher fetal concentrations ...

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A freeze‐fracture study of the guinea pig yolk sac epithelium

King

1982

Anat. Rec.

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The yolk sac epithelium functions in endocytic absorption of macromolecules from the uterine lumen and in maintaining permeability barriers between the maternal (uterine) compartment and underlying fetal compartments. In this study, cell membranes and intercellular junctions of the guinea pig yolk sac were examined using the freeze-fracture technique. Intramembranous particle (IMP) distribution and size were examined in microvilli, intermicrovillous membrane, and endocytic pits. IMPs on the P-fracture face were not evenly distributed within these membrane domains and the IMPs were of several sizes. In addition, short filamentous strands sometimes bridged between the cytoplasm and the E-face of endocytic pit membranes. These results indicated that the regions of yolk sac cell membrane involved in endocytosis did not have unusual numbers or distributions of IMPs compared to other membrane regions. The intercellular junctions between endoderm cells consisted of zonulae occludentes, gap junctions, and desmosomes. The zonula occludens usually consisted of four or five interconnected strands or ridges, and were elaborately developed where three cells abutted one another. Gap junctions were infrequent, small, and often associated with the zonula occludens. Desmosomes were observed both as typical macular structures and as more extensive, elongated structures. These results confirm previous thin-section studies of yolk sac indicating the presence of tight junctions. However, the extent of development of tight junctions does not correlate with the regard absence of a potential difference across yolk sac epithelium. The presence of gap junctions does not confirm results of previous freeze-fracture studies of other yolk sacs.

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Potential differences between mother and foetus at different gestational ages in the rat, rabbit and guinea‐pig

Cited by 38 publications

References 10 publications

Effects of potassium cyanide, strophanthin or sodium‐free perfusion fluid on the electrical potential difference across the guinea‐pig placenta perfused in situ

Effects of potassium cyanide, strophanthin or sodium‐free perfusion fluid on the electrical potential difference across the guinea‐pig placenta perfused in situ

Fetomaternal Potassium Relations in the Fetal Rat on the Twentieth Day of Gestation

A freeze‐fracture study of the guinea pig yolk sac epithelium

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