EFFECT OF CYCLIC-AMP ON UROKINASE-TYPE PLASMINOGEN-ACTIVATOR RECEPTOR AND FIBRINOLYTIC FACTORS IN A HUMAN OSTEOBLAST-LIKE CELL-LINE

We investigated the effect of cyclic AMP (cAMP) on the pericellular fibrinolytic system in NY cells. Dibutyryl cAMP (dbcAMP) or forskolin increased the level of urokinase-type plasminogen activator (u-PA) mRNA and enhanced the secretion of u-PA antigen into the conditioned medium. These agents also increased u-PA antigen on the cell surface. PA inhibitor-1 (PAI-1) antigen was inhibited by dbcAMP or forskolin. Butyrate had no effect on the production and secretion of u-PA and PAI-1. A binding assay of I-125-DFP-u-PA to NY cells revealed a single class of binding sites with a K-d of 3.85 nM and B-max of 0.89 . 10(5) binding sites/cell. The B-max was increased by dbcAMP (1 mM or 10 mM), forskolin (2 mu M or 20 mu M) of 1.0-, 1.4-, 1.2- and 1.8-fold, respectively. However, the K-d value was not changed. Furthermore, the level of mRNA for the u-PA receptor (u-PAR) was increased by these agents 1.2-, 1.7-, 1.8- and 2.5-fold, respectively. However, butyrate did not alter either the B-max or the u-PAR mRNA level. These results indicated that the pericellular fibrinolytic activity induced by u-PA/u-PAR is modulated by cAMP in osteoblast-like cells.