Assumptions made to calculate protein turnover using the arteriovenous dilution model may account for the discrepancy and care must be taken with the interpretation when using only one model in anaesthetized small animals. After prolonged starvation, however, an opposite change in disappearance rate and protein synthesis rate was observed. In conclusion, our results show that during short periods of starvation both methods give similar results. Using valine and glutamine as tracers, the enhanced amino acid turnover rates were confirmed.Ĥ. In conjunction with this, calculated bidirectional membrane transport rates were also enhanced. Using the tracer dilution model, however, the calculated protein synthesis rate across the hindquarter also increased after prolonged starvation (29 ± 7 and 68 ± 16 nmol min −1 100 g −1 body weight after 16 and 112h respectively). Hindquarter protein breakdown, calculated with the tracer dilution model, increased after 112 h starvation from 28 ± 12 to 77 ± 15 nmol min −1 100 g −1 body weight. Protein synthesis rates of the gastrocnemius muscle measured by the tracer incorporation technique decreased from 3.6 ± 0.4 after 16 h starvation to 2.2 ± 0.3 after 64 h starvation and 1.8 ± 0.4 (%/day) after 112h starvation. Whole-body phenylalanine rate of appearance decreased from 456 ± 32 after 16 h to 334 ± 34 (nmol min −1 100 g −1 body weight) after 112 h starvation. Protein synthesis rates of the gastrocnemius muscle were measured by the incorporation technique and compared with hindquarter protein turnover calculated in a two- and three-compartment arteriovenous dilution model.ģ. A primed constant infusion of l-phenylalanine was given to male Lewis rats after 16, 40, 64 and 112 h starvation. We used a starvation model to compare both techniques.Ģ. More synthesis than breakdown indicates an anabolic state that builds lean tissues, more breakdown than synthesis indicates a catabolic state that burns lean tissues. A balance between protein synthesis and protein degradation is required for good health and normal protein metabolism. Different types of proteins have very different turnover rates. The applicability in small animals has not yet been proven. In cell biology, protein turnover refers to the replacement of older proteins as they are broken down within the cell. At steady state, we can make two basic assumptions (1): for all proteins, the net change in protein levels is zero, which means that (2) the number of protein molecules produced is equal to the number of proteins lost. In this review, we distinguish between cells at steady state and those undergoing a dynamic change. In human and large animal studies the arteriovenous dilution technique is used because it enables the measurement of synthesis and breakdown rates simultaneously. Turnover Rates in Steady-State Versus Dynamic Systems. In small animals the tracer incorporation technique is mostly used to measure protein synthesis, but for degradation measurements in vitro or ex vivo settings are required. Protein loss in muscle can be caused by decreased protein synthesis, increased breakdown or both.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |