Amino acid metabolism in the ovine fetus

Lemons, James A.; Schreiner, Richard L.

doi:10.1152/ajpendo.1983.244.5.e459

Cited by 50 publications

(56 citation statements)

References 17 publications

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“…This suggests that serine and glycine have unique fetal metabolic characteristics when compared with their metabolism in the adult. These same studies in fetal sheep have shown a negligible uterine uptake of glycine but a large umbilic al release of glycine from the placenta to the fetus (20,21), and the converse for serine, a measurable net uterine uptake with no measurable release of this amino acid from the placenta to the fetus in both the mid-and late-gestation fetus (7,22,23). Ther efore, there is no apparent transfer of serine from the mother to the fetus.…”

Section: ---------------------mentioning

confidence: 91%

Pathways of Serine and Glycine Metabolism in Primary Culture of Ovine Fetal Hepatocytes

Thureen¹,

Narkewicz²,

Battaglia³

et al. 1995

Pediatr Res

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Previous in vivo studies in the ovin e fetus have demonstrat ed net serin e production by the fetal liver, a pattern not seen in the adult sheep. The goal of this study was to determine the major metabolic pathway s responsible for fetal hepatic serine production by using stable isotop e methodology in primary culture of late ges tation ovine fetal hepatocytes. Specificall y selected tracers of glycine were added to individual cultures, with production of labeled serine determin ed after 24 h of incubati on. When [1-13 C ,lglycine or [2-13 C 1 ]glycine was used as the initial tracer , serine enrichment at 24 h indic ated that approximately 30% of serine production comes from glycine. Quantitative comparison of serin e enrichme nt from these two tracers suggests that serine synthesis from glycine occurs via the combined action of the glycine cleavage enzyme system (GCE) and serine hydrox ymethyltransferase (SHMT). Using [1,2-13 C:z J5 N 1 ]glycine as the tracer, there was no sig nificant increase in M + 2 glycine in the During fetal life, amino acids are used for many functions such as precursors for prote in synthesis and metab olic fuel s, and for the sy nthesis of other carbon-and nitrogen-containing compounds including nucleic acids, glyco gen, and lipid. There is increasing evidence that fetal amino acid metabolism has unique char acteristics when compared with adult metabolism (1, 2). Som e of these differences are due to ontologie changes in organ-specific amino acid metabolism (3). In particular, there appea r to be differences in fetal hepatic serin e metabolism when compared with adult hepatic serine metabolism (2, 4-8). In the sheep, in vivo studi es have indicated that serine and glycin e have unique fetal metabolic characteristics compared with those that have been demonstrated in adult animals of other species. Using the unique abilit y to chronically catheterize the ov ine fetal liver, it has been demonstrated that in the

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Section: ---------------------mentioning

confidence: 91%

Pathways of Serine and Glycine Metabolism in Primary Culture of Ovine Fetal Hepatocytes

Thureen¹,

Narkewicz²,

Battaglia³

et al. 1995

Pediatr Res

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“…In this study, the naturally occurring opioid peptides, leu-enkephalin, dynorphin A (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11) and the synthetic peptides, DADLE, TIPP and TIPP-ψ, were incubated with the BeWo cell monolayers at 37°C. The surface area of a 12-well plate used in the metabolism study was larger than the surface area of Side-Bi-Side diffusion unit, and the degradation of the naturally occurring peptides became significant.…”

Section: Stability Of Opioid Peptides Upon Exposure To Bewo Cell Monomentioning

confidence: 99%

“…Although passive diffusion is the principal mechanism of transport across the placenta (9), several carrier-mediated transport mechanisms (e.g. for glucose, fatty acids and amino acids) have been identified (10,11). Several in vivo and in vitro models have been utilized to study the transport of substances across the placental barrier (12,13).…”

Section: Introductionmentioning

confidence: 99%

Transport and metabolism of opioid peptides across BeWo cells, an in vitro model of the placental barrier

Ampasavate¹,

Chandorkar²,

Velde³

et al. 2002

International Journal of Pharmaceutics

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. (2002) Transport and metabolism of opioid peptides across BeWo Cells, an in vitro model of the placental barrier. Int. J. Pharm. 233,[85][86][87][88][89][90][91][92][93][94][95][96][97][98] Abstract: In keeping with the advance of biotechnology, cell culture becomes an important tool for investigating the transport and the metabolism phenomena. A cell line of human origin, the BeWo choriocarcinoma cell line, was used for the study of the transport and metabolism of opioid peptides across the in vitro model of the placental barrier. Opioid peptides, both naturally occurring and their synthetic analogs, are of interest to be developed as potent analgesics and were included in this study. The apparent permeability coefficients of the peptides containing 4 to 11 amino acid or analog residues were in the range of 0.23-14.60 x 10 -5 cm/sec. The apparent permeability coefficients of these peptides were comparable to those of sucrose or dextrans, hydrophilic markers. Molecular weight and size of the peptides were inversely correlated to the permeability across the BeWo monolayers. Lipophilicity and charges of the peptides were also investigated and found to be the minor factors regulating the extent of peptide permeation. Contrasting to the transport of DPDPE peptide analog across the blood-brain barrier, the transport of DPDPE across the BeWo monolayers were not found to be via carrier-mediated transport. The major transport pathway of the opioid peptides across the BeWo monolayers was found to be via paracellular route. In metabolism studies, aminopeptidase was found to be a major enzyme type responsible for the degradation of naturally occurring peptides but not for the synthetic analogues. The finding obtained from the present study reveal the applicability of the BeWo cell line to be used as the in vitro cell culture model for the transport and metabolism screening of the opioid peptides.

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“…Over this period the partitioning of available energy between growth and oxidation remains constant, but there is a 37% decline in energy requirements per kg fetal tissue ( Table 1). Despite the magnitude of these changes in fetal metabolism, as long as maternal metabolism or placental function are not compromised the energy requirements for fetal maintenance and growth are met in equal parts by fetal uptake of glucose and amino acids (Lemons & Schreiner, 1983 9 Lemons & Schreiner (1983).…”

Section: Fetal-placental Interactionsmentioning

confidence: 99%

“…Glucose uptake can decrease by up to 30% following a 5 d period of starvation in late-gestation sheep (Lemons & Schreiner, 1983). Amino acid uptake remains unchanged but much greater proportions of amino acids are oxidized and this leads to a doubling in urea-N production.…”

Section: Maternal Nutrition and Fetal Growthmentioning

confidence: 99%