Phosphorylated derivatives of phloretin inhibit cyclic AMP accumulation in neuronal and glial tumor cells in culture.

The potencies of polyphloretin phosphate, di-4-phloretin phosphate, 4-phloretin phosphate and phloretin to inhibit the stimulation of cAMP accumulation by prostaglandins, isoproterenol and adenosine were studied in 2 clonal cell lines of CNS origin. The sequence of potency to inhibit PGE1 effects was the same in neuroblastoma (N4TG3) and human astrocytoma cells (1321N1): di-4-phloretin phosphate greater than polyphloretin phosphate greater than phloretin greater than 4-phloretin phosphate. The inhibition of PGE1 stimulated cAMP accumulation by the most prostaglandin-specific inhibitor di-4-phloretin phosphate was rapidly established after its addition, fully reversible after a 30 min preincubation period and independent of the presence of calcium. Kinetic studies of the inhibition of PGE1 effects by di-4-phloretin-phosphate suggest a different type of inhibition in 1321N1 and N4TG3 cells.