| Abstract: | The roles of calmodulin and protein kinase C in the activation of the human neutrophil respiratory burst were characterized pharmacologically. The protein kinase C inhibitors 1-(5-isoquinolinylsulfonyl)-2-methylpiperazine (H-7) and N-(2-aminoethyl)-5-isoquinolinesulfonamide (H-9) did not inhibit superoxide anion generation by neutrophils stimulated for 30 minutes with N-formyl-L-methionyl-L-leucyl-L-phenylalanine (FMLP) or 4 beta-phorbol 12 beta-myristate 13 alpha-acetate (PMA). However, H-7 did depress superoxide production during the first 5 minutes following stimulation. In contrast, the specific calmodulin antagonist N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide (W-7) and the dual calmodulin antagonist/protein kinase C inhibitor trifluoperazine (TFP) were potent inhibitors of the response throughout the 30 minute incubation. Stimulation of neutrophils with submaximal doses of FMLP or PMA failed to promote inhibition of the respiratory burst by H-7 or H-9, but did stimulate a respiratory burst response which was not inhibited by TFP or W-7. These results suggest that while protein kinase C may play a role in the initiation of the respiratory burst response, propagation of the response is dependent on calmodulin-dependent processes. The inability of TFP and W-7 to inhibit superoxide anion generation in response to submaximal stimulatory doses of FMLP or PMA suggests that calmodulin-independent processes may also be involved in activation of the respiratory burst. |
