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Changes in glutaminase activities of rat liver and kidney during pre- and post-natal development.

ABSTRACT: The activities of two phosphate-dependent glutaminase reactions characteristic of adult rat liver and kidney were determined in these organs from 2(1/2) days before to 7 days after birth and compared with the activities in the adult tissues. In the kidney, before and after birth, only the kidney type of activity was detected, and it increased in concentration in parallel with the steady growth of that organ throughout the period examined. In the liver, however, the kidney type of activity was the only one present 2(1/2) days before birth, and its concentration decreased to barely significant values by the end of the first week after birth. In contrast, the liver type of activity appeared only just before birth and increased to 60% of adult values over the next 4 days. There was no obvious relation between these changes in glutaminase type and changes in liver weight, protein content and total cell number that occurred during this time. But there was a very close correlation between the fall in kidney-type activity and the estimated fall in haematopoietic-cell number in liver.

SUBMITTER: Linder-Horowitz M

PROVIDER: S-EPMC1184796 | biostudies-other | 1969 Aug

REPOSITORIES: biostudies-other

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Project description:Skeletal growth by endochondral ossification involves tightly coordinated chondrocyte differentiation that creates reserve, proliferating, prehypertrophic, and hypertrophic cartilage zones in the growth plate. Many human skeletal disorders result from mutations in cartilage extracellular matrix (ECM) components that compromise both ECM architecture and chondrocyte function. Understanding normal cartilage development, composition, and structure is therefore vital to unravel these disease mechanisms. To study this intricate process in vivo by proteomics, we analyzed mouse femoral head cartilage at developmental stages enriched in either immature chondrocytes or maturing/hypertrophic chondrocytes (post-natal days 3 and 21, respectively). Using LTQ-Orbitrap tandem mass spectrometry, we identified 703 cartilage proteins. Differentially abundant proteins (q < 0.01) included prototypic markers for both early and late chondrocyte differentiation (epiphycan and collagen X, respectively) and novel ECM and cell adhesion proteins with no previously described roles in cartilage development (tenascin X, vitrin, Urb, emilin-1, and the sushi repeat-containing proteins SRPX and SRPX2). Meta-analysis of cartilage development in vivo and an in vitro chondrocyte culture model (Wilson, R., Diseberg, A. F., Gordon, L., Zivkovic, S., Tatarczuch, L., Mackie, E. J., Gorman, J. J., and Bateman, J. F. (2010) Comprehensive profiling of cartilage extracellular matrix formation and maturation using sequential extraction and label-free quantitative proteomics. Mol. Cell. Proteomics 9, 1296-1313) identified components involved in both systems, such as Urb, and components with specific roles in vivo, including vitrin and CILP-2 (cartilage intermediate layer protein-2). Immunolocalization of Urb, vitrin, and CILP-2 indicated specific roles at different maturation stages. In addition to ECM-related changes, we provide the first biochemical evidence of changing endoplasmic reticulum function during cartilage development. Although the multifunctional chaperone BiP was not differentially expressed, enzymes and chaperones required specifically for collagen biosynthesis, such as the prolyl 3-hydroxylase 1, cartilage-associated protein, and peptidyl prolyl cis-trans isomerase B complex, were down-regulated during maturation. Conversely, the lumenal proteins calumenin, reticulocalbin-1, and reticulocalbin-2 were significantly increased, signifying a shift toward calcium binding functions. This first proteomic analysis of cartilage development in vivo reveals the breadth of protein expression changes during chondrocyte maturation and ECM remodeling in the mouse femoral head.

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Changes in glutaminase activities of rat liver and kidney during pre- and post-natal development.

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