Official websites use. Share sensitive information only on official, secure websites. Competing Interests: The authors have declared that no competing interests exist. This is an open access article distributed under the terms of the Creative Commons Attribution License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. In vivo turnover rates of proteins covering the processes of protein synthesis and breakdown rates have been measured in many tissues and protein pools using various techniques.
Connective tissue and collagen protein turnover is of specific interest since existing results are rather diverging. The aim of this study is to investigate whether we can verify the presence of protein pools within the same tissue with very distinct turnover rates over the life-span of rats with special focus on connective tissue. The tracers were injected during fetal development Day to -2 , after birth Day 5—9 , at weaning Day 25—32 at puberty Day 54—58 and at adulthood Day — Subgroups of rats were euthanized three days after every injection period, at different time point between injection periods and lastly at day Tissue liver, muscle, eye lens and patellar tendon and blood samples were collected after euthanization.
In contrast, the connective tissue protein in the eye lens and patellar tendon of the mature rat showed detainment of tracer enrichment injected during fetal development and first living days, indicating very slow turnover. The data support the hypothesis that some proteins synthesized during the early development and growth still exist much later in life of animals and hence has a very slow turnover rate.
To allow growth and remodeling as well as functional integrity most proteins are undergoing a process of continuous turnover involving degradation of existing proteins and biosynthesis of replacement proteins.
Connective tissue and collagen protein turnover is of specific interest, since existing results on synthesis and turnover rates are conflicting. Some studies indicate that matrix collagen proteins synthesized early in life in humans are preserved into adulthood in tissues like eye lenses and tendon [ 1 , 2 ]. In contrast, other studies utilizing other techniques report that collagen protein in human tendon and muscle has a synthesis rate in adulthood [ 3 ] and in older age [ 4 , 5 ] that is comparable to e.
