Thyrotropin-releasing hormone enhances the superoxide anion production of rabbit peritoneal macrophages stimulated with N-formyl-methionyl-leucyl-phenylalanine and opsonized zymosan.

Effects of thyrotropin-releasing hormone (TRH) on the superoxide anion (O2-) production, which is essential for effective microbicidal and cytotoxic activity in macrophages (M phi s), were investigated. TRH by itself failed to induce the O2- production of rabbit peritoneal M phi s elicited with thioglycollate medium. However, M phi s preincubated with TRH showed the significant enhancements of O2- production following stimulation with the chemotactic peptide, N-formyl-methionyl-leucyl-phenylalanine (FMLP), at TRH concentrations from 10(-7) to 10(-4) M with a peak enhancement at 10(-5) M. O2- generations of M phi s stimulated with opsonized zymosan (OZ) were also enhanced at TRH concentrations from 10(-10) to 10(-5) M with a peak enhancement at 10(-7) M. Maximal enhancements of O2- production were obtained with 10 min preincubation with TRH both for FMLP and OZ stimulations. TRH had no effect on O2- production when stimulated with phorbol 12-myristate 13-acetate. Thyrotropin did not augment the O2- production induced with either FMLP or OZ. These results indicate that TRH has the priming effect on FMLP- and OZ-induced O2- production of rabbit peritoneal M phi s, although the mechanism remains to be clarified.