Calmodulin-dependency of human neutrophil phosphodiesterase.

A recent study has reported that the phosphodiesterases of human neutrophils are calmodulin-insensitive (Smolen and Geosits, Inflammation 8:193-199, 1984). In the present study, two forms of human neutrophil phosphodiesterase were separated by chromatography on DEAE-52. Peak I phosphodiesterase is activated 2.3-fold by calcium and calmodulin but is not stimulated by either calcium or calmodulin alone. Calmodulin-dependent activation of the phosphodiesterase is blocked by both 20 microM trifluoperazine and 20 microM W-7. Peak II is not stimulated by calmodulin. These findings suggest that calmodulin may play an important role in regulating alterations in cyclic nucleotide metabolism that accompany neutrophil activation.