标题：Postprandial Changes in Portal Venous Free Amino Acids and Insulin/Glucagon Ratios as the Result of Protein Over-Intake Are Not Directly Linked to Serine Dehyratase Induction in Rat Liver Irrespective of Age
期刊名称：Journal of Nutritional Science and Vitaminology
印刷版ISSN：0301-4800
电子版ISSN：1881-7742
出版年度：2003
卷号：49
期号：4
页码：247-255
DOI：10.3177/jnsv.49.247
出版社：Center for Academic Publications Japan
摘要：The activity of hepatic serine dehydratase (SDH) increases in tandem with its gene expression when the intake of protein greatly exceeds protein requirements. The actual conditions of plasma free amino acids and pancreatic hormones in weanling and mature rats when fed SDH-inducible and non-inducible diets were examined in relation to incentive factors to secure high SDH activity from a physiological standpoint. Both weanling and mature groups differing in protein requirements were allowed free access to respective diets diverse in protein content (i.e. 25% or 50% casein diet for the former and 6% or 25% casein diet for the latter) during the dark cycle (lights-out) over a period of 1 wk. Despite the difference in protein intake among these groups, there were no conspicuous changes in the plasma concentration of the urea or total or essential amino acids. Therefore, it appears that the individual amino acids did not up regulate the gene and function expressions of SDH merely by their superabundance and subsequent disposal. Portal venous insulin concentration was far higher in mature groups than in weanling groups, although there was little difference between the two groups of the same age in terms of insulin or glucagon concentration and their ratio in abdominal vena cava blood. Accordingly, it follows that the SDH gene undergoes transcriptional regulation through a combined signaling pathway triggered by perceiving surplus protein nutrition as a whole rather than directly through already-known plasma constituents such as free amino acids or pancreatic hormones in the circulatory system.
关键词：serine dehydratase induction;protein over-intake;plasma free amino acids;plasma insulin/glucagon ratio
