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

Abstract

Effects of thyrotropin-releasing hormone (TRH) on the superoxide anion (O 2 −) production, which is essential for effective microbicidal and cytotoxic activity in macrophages (Mφs), were investigated. TRH by itself failed to induce the O 2 − production of rabbit peritoneal Mφs elicited with thioglycollate medium. However, Mφs preincubated with TRH showed the significant enhancements of O 2 − 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. O 2 − generations of Mφs 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 O 2 − production were obtained with 10 min preincubation with TRH both for FMLP and OZ stimulations. TRH had no effect on O 2 − production when stimulated with phorbol 12-myristate 13-acetate. Thyrotropin did not augment the O 2 − production induced with either FMLP or OZ. These results indicate that TRH has the priming effect on FMLP- and OZ-induced O 2 − production of rabbit peritoneal Mφs, although the mechanism remains to be clarified.