Y Mussaddeq, A J El Haj.
Alkaline phosphatase activity and gene expression in rat calvaria during postnatal development.
J Pak Inst Med Sci Jan ;8-12:606-14.

Osteoblasts are rich in the plasma membrane bound enzyme alkaline phosphatase (EC 3.1.3.1 AP) which is involved in . bone formation and mineralization. Many studies have demonstrated changes in total alkaline phosphatase in plasma as a function of the subjects physiological state especially related to age. In this study we investigate the variation in bone AP with calvarial development in albino Wister rats of five different age groups. A gradual decline in AP levels was observed with increasing age suggesting an elevated rate of osteoblastic activity in young animals which decline with the growth and maturation of the animal. Correlated with the reduction in enzyme levels the AP mRNA levels decreased with age ; the highest levels of APmRNA are found in the youngest animals indicating that in vivo AP gene expression declines as mineralization progress. A decline in mg protein/g of bone was measured while there was an overall increase in ugDNA/g was observed with age. A decline in AP/ug of DNA was observed from 21 day foetuses to adults demonstrating the decrease in cellular levels of AP activity.

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