par Camus, Jean Claude 
;Vandermeers-Piret, Marie-Claire ;Wodon, Claude ;Christophe, Jean
Référence European journal of biochemistry / FEBS, 11, 2, page (225-233)
Publication Publié, 1969
;Vandermeers-Piret, Marie-Claire ;Wodon, Claude ;Christophe, Jean Référence European journal of biochemistry / FEBS, 11, 2, page (225-233)
Publication Publié, 1969
Article révisé par les pairs
| Résumé : | 100 g rats, submitted for 3 weeks to protein malnutrition (mostly lysine and threonine deficiency) with a diet offered ad libitum but containing 7% gluten as the sole protein, were starved for 24 h and allowed to recover for 3 days on a diet containing 18% casein and 0.3%dl‐methionine. These animals were compared to control rats refed on the gluten diet. The food intake as well as the level of immunoreactive plasma insulin increased immedieately. Among the free amino acids of the plasma, lysine, threonine and tyrosine rose rapidly (4‐ to 6‐fold), others were also significantly elevated while serine, glycine and histidine decreased. In the liver, the concentration of taurine was multiplied 7‐fold, that of threonine tripled, those of lysine, leucine, isoleucine, valine, tyrosine and phenylalanine doubled approximately, while the level of serine was markedly decreased. After 3 days, the total protein and DNA contents had increased by 70% and 2% respectively. Protein concentration on a wet weight basis was slightly higher than that observed in rats maintained on gluten whereas glycogen concentration levelled at a significantly lower (–43%) value. Of the 13 enzymatic specific activities investigated for their contribution to the intermediary metabolism, some did not vary significantly (α‐amylase bound to glycogen, hexokinases 1, 2 and 3, NADP:malate dehydrogenase, ATP:citrate lyase, arginase). Five activities increased (glucokinase 4‐fold, glucose‐6‐phosphate dehydrogenase 6‐fold, 6‐phosphogluconate dehydrogenase 2‐fold, serine dehydrogenase 2‐fold and ornithine aminotransferase 8‐fold) and three activities decreased somewhat (pyruvate kinases 0.60‐fold, glucose‐6‐phosphatase 0.65‐fold and fructose‐1,6‐diphosphatase 0.70‐fold). These rapid modifications might favour in the liver (a), a faster utilization of glucose in the two main glycolytic pathways; (b), a decrease in the hepatic glucose output and (c), the removal of the amino group of amino acids supplied in excess of the needs for protein storage. From these results and previously published experiments it thus appears that within the 3 days following a period of amino acid imbalance, insulin hypersecretion could not only have general effects on protein synthesis and turnover and on mitotic activity but might also be specifically involved in the induction of glucokinase and glucose‐6‐phosphate dehydrogenase and in the repression of glucose‐6‐phosphatase and fructose‐1,6‐diphosphatase. The influx of free amino acids plays the main role in the induction of serine dehydratase and ornithine aminotransferase and could share the responsability with insulin in the induction of glucokinase and glucose‐6‐phosphate dehydrogenase. Copyright © 1969, Wiley Blackwell. All rights reserved |
