Substrate Metabolism and Interrelationships in the Ovine Fetus in Utero

Kitts, David D.; Krishnamurti, C. R.

doi:10.4141/cjas82-046

Cited by 8 publications

(7 citation statements)

References 11 publications

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“…Hems, 1977). However, there was no evidence from the present work of significant production of glucose from lactate in the conceptus, supporting an earlier premise (Hodgson et al 1980) that lactate did not contribute to the synthesis of glucose by the conceptus (see also Warnes et al 1977;Kitts & Krishnamurti, 1982;Sparks et al 1982;396 1985;Gu, Jones & Harding, 1987), the Cori cycle appears not to operate in the ovine conceptus.…”

Section: Discussionsupporting

confidence: 65%

“…There was no direct contribution of maternal glucose carbon to the lactate pool of the conceptus and, thus, the present results do not support the concept of an exogenous carbon supply to the conceptus in the form of lactate derived from maternal glucose during transfer from maternal to fetal blood. Lactate and glucose transactions within the conceptus The rate of lactate irreversible loss from the conceptus (5 1 +0 7 mg carbon min-1 (kg fetus)-1) was higher than other published values of between 2-2 and 3*1 mg carbon min-(kg fetus)`1 (Warnes, Seamark & Ballard, 1977;Prior, 1980;Kitts & Krishnamurti, 1982;Sparks et al 1982). This is consistent with the observed positive correlation between the rates of lactate use and umbilical glucose uptake by the fetal sheep (Sparks et al 1982) and the high rate of transfer of glucose from mother to conceptus obtained in the present work.…”

Section: Discussionmentioning

confidence: 53%

“…The net input of lactate from the sheep uteroplacenta to the fetus (Burd, Jones, Simmons, Makowski, Meschia & Battaglia, 1975;Char & Creasy, 1976) has been referred to as an exogenous supply of fetal carbon (Battaglia & Meschia, 1978;Sparks, Hay, Bonds, Meschia & Battaglia, 1982), implying that it comprises carbon 'new' to the fetal circulation. The relative impermeability of the sheep uteroplacenta to lactate (Britton, Huggett & Nixon, 1967) restricts the origin of any uteroplacental lactate input comprising carbon new to the conceptus to lactate derived from maternal substrates, primarily glucose (Sparks et al 1982) and amino acids (Prior & Christenson, 1977;Kitts & Krishnamurti, 1982), during transfer from the mother, However, there is little loss of amino acids during transfer from the mother across the uteroplacenta (Meschia, Battaglia, Hay & Sparks, 1980). On the other hand glucose is consumed in large amounts by the uteroplacenta (Simmons, Battaglia & Meschia, 1979;Meschia et al 1980) and is a probable precursor of lactate entering the umbilical circulation.…”

Section: Introductionmentioning

confidence: 99%

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Kinetics of lactate and glucose metabolism in the pregnant ewe and conceptus

Hodgson

Field²

1991

Experimental Physiology

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Two monotocous and two ditocous ewes were infused at 124-130 days of gestation with a mixture of L-[U-14C]lactate and D-[6-3H]glucose via a maternal or umbilical catheter, separate days being used for each infusion. Plateaux-specific radioactivities of plasma lactate and glucose were used to derive a four-pool model describing the fluxes between the lactate and glucose pools of the infused conceptus and mother. The average turnover rate of lactate was 23.3 and 13.2 mg carbon min-1 in the conceptus and 32.0 and 44.0 mg carbon min-1 in the mother for monotocous and ditocous ewes, respectively. Glycolysis rates within both conceptus and mother in all sheep were high, accounting for about 80 and 60% of the respective rates of lactate turnover. The synthesis of glucose from lactate accounted for 13 and 31% of the glucose turnover in the mother in monotocous and ditocous ewes, respectively, but was insignificant in the conceptus. Glycolysis within the conceptus used only glucose which had entered and mixed with the conceptus glucose pool; there was no direct transfer of carbon from the maternal glucose pool to the conceptus lactate pool. This finding is an important validation for the use of tracer methods to determine glucose use within the whole conceptus rather than within fetal corporeal tissues alone.

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Section: Discussionsupporting

confidence: 65%

Section: Discussionmentioning

confidence: 53%

Section: Introductionmentioning

confidence: 99%

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Kinetics of lactate and glucose metabolism in the pregnant ewe and conceptus

Hodgson

Field²

1991

Experimental Physiology

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“…Similar or related 'two-pool' models have been used for assessment of lactate and amino acid metabolism in the 'fetus' without any apparent account having been taken of the metabolic activity of the placenta and other membrane structures of the conceptus or their interrelations with the fetal body (Kitts & Krishnamurti, 1982;Schaefer & Krishnamurti, 1982.…”

Section: Vol 45mentioning

confidence: 99%

Nutrition of the conceptus: aspects of its regulation

Bassett

1986

Proc. Nutr. Soc.

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“…Their value of 001 mmol progesterone/day at 118-135 days of gestation is significantly less than the potential rate of metabolism by fetal blood. Also, to provide 3 mmol NADPH only 1-5 mmol glucose need be metabolized through the pentose-phosphate pathway (Rapoport, 1968) which represents < 1% of the estimated fetal glucose require¬ ment of 170-240 mmol/day (Prior & Christenson, 1977;Warnes, Seamark & Ballard, 1977;Hay, 1979;Sparks, 1979;Hodgson, Mellor & Field, 1980;Kitts & Krishnamurti, 1982;Sparks, Hay, Bonds et al 1982). This percentage would be higher if expressed as a proportion of glucose utilization by erythrocytes but data are not available to establish this relationship.…”

Section: Discussionmentioning

confidence: 99%

Relationship between glucose and 20α-hydroxysteroid dehydrogenase in fetal sheep erythrocytes

Nancarrow¹,

Connell²,

Stevens³

1984

Journal of Endocrinology

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We have examined whether glucose supply to fetal sheep erythrocytes limits the rate of 20 alpha-reduction of progesterone in blood and as such is associated with the progressive loss of 20 alpha-hydroxysteroid dehydrogenase activity which has been observed from 30 days before term. Enzyme activity in erythrocytes depleted of glucose by washing was regained in the presence of at least 0.167 mmol glucose/1. The cofactor NADPH was necessary to support the reaction in lysed cells. Addition of glucose to whole blood diluted 20-fold for assay of 20 alpha-hydroxysteroid dehydrogenase did not increase the rate of reaction. Infusion of dextrose to increase fetal plasma glucose concentrations had no effect on 20 alpha-hydroxysteroid dehydrogenase activity. Over the period from 114 to 137 days of gestation, both dextrose- and saline-infused fetuses showed a decline in enzyme activity from a combined mean of 1.45 +/- 0.21 (S.E.M.) to a mean of 0.78 +/- 0.18 mumol/ml erythrocytes per h. Fetal leucocytes did not contribute significantly to the activity of 20 alpha-hydroxysteroid dehydrogenase in whole blood. The rate of 20 alpha-reduction of progesterone in the blood of eight fetuses with indwelling carotid catheters declined from 2.31 +/- 0.09 mumol/ml erythrocytes per h at 90-95 days of gestation to 0.73 +/- 0.04 mumol/ml per h at 141-145 days. However, a consistent decline was only observed after 116-120 days. The apparent equilibrium position for progesterone reduction to 20 alpha-dihydroprogesterone varied between 83.9 +/- 1.8 and 65.7 +/- 4.2%.(ABSTRACT TRUNCATED AT 250 WORDS)

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Substrate Metabolism and Interrelationships in the Ovine Fetus in Utero

Cited by 8 publications

References 11 publications

Kinetics of lactate and glucose metabolism in the pregnant ewe and conceptus

Kinetics of lactate and glucose metabolism in the pregnant ewe and conceptus

Nutrition of the conceptus: aspects of its regulation

Relationship between glucose and 20α-hydroxysteroid dehydrogenase in fetal sheep erythrocytes

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