cDNA cloning of alkaline phosphatase from rat osteosarcoma (ROS 17/2.8) cells.

Two cDNA clones of rat alkaline phosphatase (AP) were isolated from a rat osteosarcoma lambda gt 11 cDNA library (ROS 17/2.8) utilizing a human bone-liver-kidney (BLK) type AP cDNA. These clones contain overlapping DNA sequences of 597 and 520 bp, respectively, corresponding to the 3' noncoding region of AP mRNA. The sequence homology with the human BLK AP cDNA is 61%. In Northern blot analysis the rat cDNA hybridizes to a single band of 2.5 kb mRNA from ROS 17/2.8 and rat liver, under highly stringent conditions. Steady state levels of AP mRNAs measured in several rat osteosarcoma cell lines (ROS 17/2.8, ROS 2/3, ROS 25/1, UMR 106) correlate with the level of AP enzymatic activity in these cells. Dexamethasone, which stimulates AP enzymatic activity in ROS 17/2.8 cells, increases the relative abundance of AP mRNA in a dose-dependent manner. This probe can be used to study AP expression in rat tissues and cells.