Objective: To investigate the characteristics of urotensin II (U-II) receptor in the rat airway smooth muscle and the effect and signal transduction pathway of U-II on the proliferation of airway smooth muscle cells.
Methods: Using 125I-UII binding assay to measure the Bmax and Kd of U-II receptor. Using the 3H-TdR incorporation to determine the effect of U-II on the proliferation of airway smooth muscle cells and its signal transduction pathway. Using Fura-2/AM to measure the effect of U-1I on the cytosolic free calcium concentration.
Results: 1. 125I-UII binding increased with the time and reached saturation at 45 min. The B(max0 was (11.36 +/- 0.37)fmol/mg pr and Kd was (4.46 +/- 0.61) nmol/L. 2. U-II increased 3H-TdR incorporation of the airway smooth muscle cells in a dose-dependent manner. 3. H7, PD98059 and nicardipine, inhibitors of PKC, MAPK, calcium channel, respectively, significantly inhibited U-II-stimulated 3H-TdR incorporation of airway smooth muscle cells. W7, inhibitor of CaM-PK, had no effect. 4. Cyclosporin A, inhibitor of CaN, inhibited 3H-TdR incorporation of the airway smooth muscle cells induced by U-II in a dose-dependent manner. 5. U-II promoted cytosolic free calcium concentration increase by 18%.
Conclusions: 1. There was U-II receptor in the rat airway smooth muscle. 2. The effect of U-II-stimulated 3H-TdR incorporation of airway smooth muscle cells was mediated by such signal transduction pathway as Ca2+, PKC, MAPK and CaN, etc.