The transfer of free α‐amino nitrogen across the placental membrane in the guinea‐pig

Abstract

SUMMARY1. Transfer of endogenous a-amino nitrogen from the maternal to foetal side of the placental membrane was studied in the foetal guinea-pig placenta perfused, in situ via the umbilical vessels, with an artificial fluid. Changes in maternal placental blood flow were followed by measuring the transfer of antipyrine into the perfusate.2. Active transport by the membrane was demonstrated under these conditions by observing the increased ratio of L/D leucine appearing in the perfusate in comparison with the maternal plasma ratio.3. Reduction in maternal placental flow following haemorrhage was associated with a fall in transfer of amino nitrogen to about half of the control values.4. The concentration of ax-amino nitrogen in the perfusate was inversely proportional to the foetal placental flow which had a smaller influence on amino nitrogen transfer per min than did the maternal blood flow.5. Hypoxia and some inhibitors of oxidative metabolism were without influence on the transfer of a-amino nitrogen in this preparation.

Diabetes in Pregnancy: Decreased Placental Blood Flow and Disturbed Fetal Development in the Rat

“…Although a number of estimations of placental blood flow in rodents have been reported (I , 2,5,7,15,16,27,29,34), no studies of placental blood flow in diabetic rat pregnancy seem to have been published. There are, however, reports of altered placental morphology (26) and indirect evidences of changed vascular function in diabetic rat placenta (4) as well as decreased transfer of aminoisobutyric acid to fetuses ofdiabetic guinea pigs (30).…”

“…Disturbances in the transfer of nutrients from mother to fetus, reflecting altered placental funct ion, may be of importance for the decreased somat ic growth rate (17,18). Besides, the magnitude of the placental blood flow determines the amount of nutrients available for transfer to the fetus (27). Therefore , placental blood flow may be relevant to fetal growth retardation (28).…”

Placental transfer and fetal uptake of amino acids in the pregnant ewe

“…The differences strengthened by the findings, in the perfused between fetal and maternal plasma are mostly guinea pig placenta, that amino acid transfer is due to different amino acid metabolic equil-independent of flow on the fetal side of the bria on each side of the placental membrane;. placenta, when this is varied within physiological in the guinea pig, with the fetal placenta perfused limits; at very low flows, the placental secretion 'in situ', the amino acid pattern of the perfusate causes a marked rise in their concentrations in the was different from that of the fetal plasma and umbilical vein plasma (REYNOLDS and YOUNG resembled the composition of maternal plasma [31]). The faster transfer rates of the neutral (YouNG [38]).…”

Proceedings of the British Pharmacological Society

“…Constant infusions were maintained, via the maternal jugular vein, of: (1) metaraminol (Aramine) to maintain and steady the maternal arterial pressure and placental circulation, and (2) of antipyrine (Phenazone) to monitor changes in the maternal placental blood flow. When the maternal arterial pressure and acid base balance were within the normal ranges, there was close agreement between the perfusate and maternal plasma concentrations of antipyrine; in a poor preparation or following maternal haemorrhage, there was a reduction in the antipyrine transfer (Reynolds & Young, 1971). Therefore, the transfer of antipyrine may be used as an index of maternal placental blood flow, and to determine whether the pharmacological effect of a drug on the transfer of another substance is direct, or mediated by changes in the maternal placental circulation.…”

“…Details of a simple modification of Money & Dancis' preparation have been described (Reynolds & Young, 1971). Briefly, the near term mother was anaesthetized with pentobarbitone sodium (Nembutal, 20-30 mg/kg) and supported in a saline bath at 38°C.…”