DETERMINATION OF PHOSPHODIESTERASE ACTIVITY IN RAT MAST-CELLS USING THE FLUORESCENT CAMP ANALOG ANTHRANILOYL CAMP

Cyclic AMP and the isozyme families that control its concentration hav e an important role in rat mast cells, We have attempted to determine the total phosphodiesterase activity in rat mast cells by means of spe cific and non-specific inhibitors of phosphodiesterases. We used a flu orescent analogue of cAMP, 2'-O-anthraniloyl cAMP, the fluorescence in tensity of which decreases when hydrolysed by phosphadiesterase (PDE), providing a measurement of total activity of PDE. The PDE inhibitors produced a decrease in the fluorescence fall. Therefore, we can establ ish that at least Type I, III, IV and probably Type V PDE are present in rat mast cells. We have also studied the effect of these PDE inhibi tors on histamine release elicited by compound 48/80 and sodium fluori de. Chlorpromazine, a Type I PDE inhibitor, only slightly inhibits the fluoride-evoked response, while, on the other hand, milrinone, a Type III PDE inhibitor, does not modify the response to compound 48/80.