Size of L-Lactate Transport from the Fetal Rat to the Mother Animal

Kraan, G.P.B.; Dias, T.

doi:10.1159/000240713

Cited by 11 publications

(3 citation statements)

References 16 publications

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“…Since L-lactate transfer should occur either from maternal to fetal blood or vice versa, it is likely that the reversibility of the carrier would represent a physiological mechanism for the transfer of L-lactate between both compartments. Thus at the end of gestation the L-lactate produced by the fetus must then be transported to the maternal circulation (Kraan & Dias, 1975).…”

Section: Concentration-dependence Of L-lactate Uptakementioning

confidence: 99%

Carrier-mediated l-lactate transport in brush-border membrane vesicles from rat placenta during late gestation

Torre

Serrano

Alvarado

et al. 1991

Biochemical Journal

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The mechanism for L-lactate transport across microvillous membrane vesicles prepared from rat placenta was examined. Uptake of L-lactate into these vesicles was mainly the result of transport into the intravesicular (osmotically active) space. The initial rate of L-lactate uptake was not affected by the presence of an inward gradient of either Na+ or K+. In the presence of an inward-directed proton gradient, L-lactate uptake was markedly stimulated, accumulating at concentrations 6-7-fold higher than the equilibrium. Lower transmembrane pH gradients were associated with slower initial uptakes and smaller overshoots. L-Lactate uptake determined under an inside-directed pH gradient was strongly inhibited by p-chloromercuriphenylsulphonic acid, a protein-thiol oxidizing agent. L-Lactate uptake was: (1) saturable as a function of the concentration of L-lactate, (2) inhibited by monocarboxylic acids such as pyruvate, D-lactate, /-hydroxybutyrate and a-cyano-4-hydroxycinnamic acid, and (3) temperature-dependent. When present inside the vesicles, L-lactate, pyruvate and fl-hydroxybutyrate caused trans-stimulation of L-lactate uptake both in the presence and in the absence of an insidedirected pH gradient, indicating that L-lactate transport is a reversible process that can be shared by other monocarboxylic acids. There were no significant changes in maximal initial rate or in the kinetic parameters of L-lactate transport during the last 3 days of gestation. INTRODUCTIONThe role played by L-lactate as an important metabolic fuel for the fetus and newborn is supported by a considerable body of evidence. Thus lactate is utilized by fetal tissues as a source of energy and carbon skeletons (see Medina et al., 1990). Actually, lactate is actively utilized by perinatal brain in the rat (Itoh &

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Section: Concentration-dependence Of L-lactate Uptakementioning

confidence: 99%

Carrier-mediated l-lactate transport in brush-border membrane vesicles from rat placenta during late gestation

Torre

Serrano

Alvarado

et al. 1991

Biochemical Journal

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“…[ATP]/[A DP] ratio in isolated foetal rat liver cells as a function oJ the age of the foetus In [ATP]/[ADP] ratios in foetal rat liver cells are generally higher than those reported by others for freezeclamped foetal livers (Ballard, 1970(Ballard, ,1971bPhilippidis & Ballard, 1970;Hommes, 1971;Knowles & Ballard, 1974;Kraan & Dias, 1975). The large variation in…”

Section: Digitonin Methodsmentioning

confidence: 82%

“…[ATP]/[ADP] ratios ranging from 1.5 to 5.7 have been reported (Ballard, 1970(Ballard, , 1971 b; Philippidis & Ballard, 1970; Hommes, 1971;Knowles & Ballard, 1974;Kraan & Dias, 1975). These data were obtained by using the freeze-clamp technique, and therefore represent the ratio for total intracellular adenine nucleotides.…”

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confidence: 99%

Adenine nucleotides in foetal rat liver cells. Compartmentation and variation with age

Lelyveld¹,

Hommes²

1978

Biochemical Journal

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The digitonin method for the separation of cytosolic and mitochondrial fractions was applied to liver cells isolated from foetal rats. The cytosolic [ATP]/[ADP] ratio approximately doubles during the last 4 days of gestation, whereas the mitochondrial ratio remains constant. In the presence of oligomycin and added glucose, the cytosolic [ATP]/[ADP] ratio does not increase with age, but is still considerably higher than the mitochondrial ratio. Without added glucose, and when the glycogen content of foetal liver is still very low (more than 3 days before birth), the cytosolic [ATP]/[ADP] ratio in the presence of oligomycin becomes very low and equal to the mitochondrial ratio. It is concluded that the increasein the cytosolic [ATP]/[ADP] ratio during the last 4 days of gestation is solely due to enhanced mitochondrial activity in this period. Atractyloside and bongkrekic acid do not influence the O2 consumption, nor the [ATP]/[ADP] ratios in either compartment of foetal liver cells. Respiration of isolated foetal mitochondria, however, is strongly inhibited by both compounds. The implications of these findings are discussed.

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