RECOMBINANT HUMAN PROLACTIN INDUCES PROTECTION AGAINST SALMONELLA-TYPHIMURIUM INFECTION IN THE MOUSE - ROLE OF NITRIC-OXIDE

In the present study, we demonstrated that repeated treatment with rec ombinant human prolactin (rhPRL) protected mice against Salmonella typ himurium infection. The protective activity was statistically signific ant, dose-dependent and present only when rhPRL treatments were perfor med before the infection. This activity was probably related to the ob served increases in phagocytosis and intracellular killing of peritone al macrophages induced by the hormonal treatment. The number of periph eral leukocytes was not modified, excluding a mobilization of cells fr om other compartments. A decrease in the mortality rate after challeng e was also observed in mice treated with the monoclonal antibody anti- PRL receptor U5, confirming that the protective activity was associate d with receptor activation. Our studies also suggest that nitric oxide (NO) production was involved in the protective effect of rhPRL, since pre-treatment of the animals with L-NAME, an inhibitor of NO-synthase , was able to completely revert the protective activity, whereas D-NAM E, the inactive D-isomer, was without effect.