since methylation of the 1-position of each 3-alkylxanthine increased the potency of the derivative in inhibiting low km cyclic amp pde and in relaxing trachealis muscle and since a strong positive correlation was observed between the relaxant ec50 and the ki value of each xanthine derivative , it is suggested that low km cyclic amp pde inhibition by xanthines plays an important role in their tracheal relaxant effect .
C0043314
derivative
C0043318
xanthines