Carbohydrate metabolism in the sheep placenta

Britton, H.G.; Huggett, A. St. G.; Nixon, D. A.

doi:10.1016/0304-4165(67)90002-5

Cited by 37 publications

(29 citation statements)

References 13 publications

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“…Past experiments were aimed at evaluating fetal or maternal lactate flow and indicated that the sheep placenta was impermeable to lactate (3,4). Movement of lactate from the fetus to the ewe was seen only at extremely high, abnormal fetal lactate levels (4).…”

Section: Discussionmentioning

confidence: 99%

Lactate and Pyruvate as Fetal Metabolic Substrates

Char

Creasy

1976

Pediatr Res

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Section: Discussionmentioning

confidence: 99%

Lactate and Pyruvate as Fetal Metabolic Substrates

Char

Creasy

1976

Pediatr Res

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“…According to Hers (1960b) the conversion of glucose to sorbitol takes place in the placenta, and the subsequent conversion of sorbitol to fructose is carried out in the fetal liver. However, Britton, Huggett & Nixon (1967) in experiments of placental perfusion with labelled glucose showed that the ovine placenta is capable of converting glucose to fructose. The present study confirms that the placenta is a source of fetal fructose by showing that during the infusion of tracer fructose into the fetus, the specific activity of fructose in umbilical venous blood was significantly less than in umbilical arterial blood.…”

Section: Discussionmentioning

confidence: 99%

Fructose Disposal and Oxidation Rates in the Ovine Fetus

et al. 1987

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SUMMARYFructose disposal and oxidation rates were measured in fetal lambs receiving a constant intravenous infusion of D-[U-'4C]fructose. Approximately 60 % of the infused tracer entered the placenta, but loss of fructose into the maternal circulation was negligible. Fructose was metabolized to lactate and CO2 in both the placenta and fetus, whereas there was no detectable conversion to glucose. In well-fed ewes the fetal disposal and utilization rates of fructose were 2-41 + 017 and 097 + 0-09 mg/min.kg, respectively. The umbilical excretion rate of CO2 originating from the oxidation of fetal fructose was 18-1 + 13 1smol/min.kg or 5-3 % of total fetal CO2 production. This excretion rate is one-fifth of the CO2 excretion rate from fetal glucose carbon. In four ewes comparison of fructose metabolism in the fed and fasted states showed a significant decrease of fructose production and oxidation with fasting. Although fructose is present in high concentrations in the fetal blood of ungulates, its contribution to fetal oxidative metabolism is relatively small in comparison to glucose.

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“…The high concentration of fructose in the blood of fetal lambs was demonstrated many years ago [Bacon and Bell, 1946;Cole and Hitchcock, 1946] and fetal fructose is formed in the placenta from glucose [Huggett, Warren and Warren, 1951;Alexander, Huggett and Widdas, 1951;Alexander, Andrews, Huggett, Nixon and Widdas, 1955;Britton, Huggett and Nixon, 1967]. All the evidence to date suggests that this sugar is not metabolized to any great extent by the lamb [Huggett, 1961;Alexander, Britton and Nixon, 1966;Alexander, Britton, Cohen and Nixon, 1969].…”

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confidence: 99%

The Importance of Glucose in the Oxidative Metabolism of the Pregnant Uterus and Its Contents in Conscious Sheep With Some Preliminary Observations on the Oxidation of Fructose and Glucose by Fetal Sheep

Setchell¹,

Bassett²,

Hinks³

et al. 1972

Exp Physiol

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The day after implantation of catheters under general anaesthesia, u-[14C] glucose was infused intravenously into four conscious ewes about 130 days pregnant, and into two fetuses about 130 days old. u-[14C] fructose was infused into three other similar fetuses.It could be calculated that the pregnant uterus with its contents derived about 40% of its CO2 from blood glucose and oxidized directly about 45% of the glucose utilized. The total uptake of glucose by the uterus and contents accounted for about 70% of the glucose metabolism of the pregnant ewes, but the proportion of C02 derived by the pregnant ewes from glucose was no higher than for non-pregnant ewes or rams. The total oxygen consumption of uterus and contents was comparable to the extra oxygen used by a ewe when pregnant, as measured by calorimetry. The specific radioactivity of fetal blood fructose was still only about 60% of that of maternal blood glucose after 5 hours infusion which suggests that there are other precursors for fetal fructose besides maternal glucose.[14C] from fructose and glucose infused into the fetus was converted into C02 and glycogen and [14C] from fructose was converted to glucose by the fetus or placenta. The degree of incorporation of both sugars into C02 and glycogen was similar but neither sugar could account for more than a fraction of the CO2 production.It has been stated [Kronfeld, 1958;Reid, 1968] that the pregnant uterus is a major user of glucose in the body and that most of its oxidative metabolism depends on blood glucose. In the present experiments an attempt has been made to put these deductions on a quantitative basis in conscious animals.In addition, some preliminary experiments are reported in which we measured the rate of fetal utilization of fructose in conscious animals. The high concentration of fructose in the blood of fetal lambs was demonstrated many years ago [Bacon and Bell, 1946;Cole and Hitchcock, 1946] and fetal fructose is formed in the placenta from glucose [Huggett, Warren and Warren, 1951;Alexander, Huggett and Widdas, 1951;Alexander, Andrews, Huggett, Nixon and Widdas, 1955;Britton, Huggett and Nixon, 1967]. All the evidence to date suggests that this sugar is not metabolized to any great extent by the lamb [Huggett, 1961;Alexander, Britton and Nixon, 1966;Alexander, Britton, Cohen and Nixon, 1969]. Alexander, Britton and Nixon [1970] have shown that in the isolated perfused fetus only about 3% of the CO2 production came from fructose, and they suggested that glucose was probably the major fetal metabolite. However, we have shown that [14C] from

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Carbohydrate metabolism in the sheep placenta

Cited by 37 publications

References 13 publications

Lactate and Pyruvate as Fetal Metabolic Substrates

Lactate and Pyruvate as Fetal Metabolic Substrates

Fructose Disposal and Oxidation Rates in the Ovine Fetus

The Importance of Glucose in the Oxidative Metabolism of the Pregnant Uterus and Its Contents in Conscious Sheep With Some Preliminary Observations on the Oxidation of Fructose and Glucose by Fetal Sheep

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