Difference in Electric Potential Across the Placenta of Goats

SUMMARY1. Fifteen sheep foetuses of 1-5-5-2 kg body weight were prepared with indwelling arterial and venous catheters for experimentation one to six days later.2. Unanaesthetized foetuses were found to have mean arterial and central venous blood pressures of 40 + 1-5 (S.E. of mean) and 2x0 + 0-3 (S.E. of mean) mm Hg respectively, compared to intra-uterine pressure. Intra-uterine pressure was 16 + 0-8 (S.E. of mean) mm Hg with respect to atmospheric pressure at mid-uterine level.3. Mean placental blood flow of the foetuses was 199 + 20 (S.E. of mean) ml./(min. kg body wt.). Mean cardiac output in eleven of the foetuses was 658 + 102 (S.E. of mean) ml./(min.kg).4. Mean foetal and maternal colloid osmotic pressures were 17'5+ 0 7 (S.E. of mean) and 20-5 + 0-6 (S.E. of mean) mm Hg respectively at 380 C.5. Intravenous infusions into six ewes of 1P8 mole of mannitol and 0 4 mole of NaCl resulted in significant increases in foetal plasma osmolarity, sodium, potassium, and haemoglobin concentrations, without detectable transfer of mannitol to the foetal circulation.6. In the sheep placenta there is osmotic and hydrostatic equilibration of water. As a consequence, there should be an interaction between foetal placental blood flow and foetal water exchange with the maternal circulation. It was concluded that this interaction tends to stabilize foetal placental blood flow.

Section: Discussionmentioning

confidence: 99%

Foetal placental blood flow in the lamb

Faber¹,

Green²

1972

“…Observation of p.d.s between maternal tissues and conceptuses of different species, therefore, could yield important information relating to the supply of ions to the foetus. Reports of such p.d.s are restricted to the goat (Meschia, Wolkoff & Barron, 1958), the sheep and cat (Widdas, 1961), the rabbit (Wright, 1963), and the chorioallantoic membrane of the pig (Crawford & McCance, 1960). The object of the present study was to compare the p.d.s associated with the fluid compartments * Research Scholar, University of Edinburgh.…”

Section: Introductionmentioning

confidence: 98%

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

Mellor¹

1969

SUMMARY1. Potential differences associated with fluid compartments of rat, rabbit and guinea-pig conceptuses have been measured. [Na+] and [Cl-] in maternal plasma and amniotic fluid from these three species were also determined.2. Transplacental potential differences of about 15 mV (foetus positive) were found in the rat, of approximately 0 mV in the rabbit, and of about 18 mV (foetus negative) in the guinea-pig.3. Amniotic fluid potential differences appeared to arise indirectly from the transplacental potential difference in the rat, from the foetal gastric mucosa in the rabbit, and possibly from the foetal gastric mucosa and indirectly from the placenta in the guinea-pig.4. The results are discussed in the context of Na+ transfer to the foetus, and on this basis tend to question the general assumption that almost all Na+ reaching the foetus passes across the placenta.

“…Details of the ionic composition of goat foetal fluids do not seem to be available, but sheep foetal fluids have been examined (Malan, Malan & Curson, 1937; Cloete, 1939;McDougall, 1949), and possible relationships between their composition and that of foetal urine and foetal and maternal plasma have been suggested (Alexander, Nixon, Widdas & Wohlzogen, 1958a). When these observations were made details of electrochemical gradients between maternal and foetal plasma and amniotic and allantoic fluid were not available, and subsequent work in the goat (Meschia, Wolkoff & Barron, 1958) and sheep (Widdas, 1961) was relatively limited. The object of the present study was to investigate the potential difference (p.d.…”

Section: Introductionmentioning

confidence: 99%

Distribution of ions and electrical potential differences between mother and foetus at different gestational ages in goats and sheep

Mellor¹

1970

SUMMMARY1. Potential differences associated with the compartments of goat and sheep conceptuses have been measured in vivo and in vitro during the last half of gestation and the osmolarity, and the [Na+], [K+], and [CO-] of maternal and foetal plasma and amniotic and allantoic fluid taken from these animals were determined.2. The potential difference (p.d.) patterns of both goats and sheep were the same.(a) The transplacental p.d. was about 71 mV (foetus negative) in the goat, and about 51 mV (foetus negative) in the sheep. 3. The ionic concentrations were considered in relation to the electrochemical gradients found between the maternal and foetal fluid compartments to determine whether the ions were distributed according to electrochemical equilibrium. DA VID J. MELLOR (a) It seems that ions in the amniotic fluid tend to equilibrate with foetal plasma, and not with maternal plasma or allantoic fluid, that changes in the [Na+] and [K+] of amniotic fluid can be accounted for largely in terms of passive factors, and that variations in the [Cl-] are associated with activity of an electrogenic Cl-pump directed from the foetal blood into the amniotic fluid.(b) It appears that ions in the allantoic fluid can exchange with those of both maternal and foetal plasma, that an electrogenic pump effects absorption of Na+ from the allantoic fluid into the foetal blood, and that the [K+] and [Cl-] of allantoic fluid are maintained largely by passive exchange under the action of electrochemical gradients between maternal plasma and allantoic fluid, and between foetal plasma and allantoic fluid.4. The results considered in the context of Na+ passage between mother and foetus call in question the general assumption that all Na+ reaches the foetus by passing across the placenta.