It has been demonstrated that prolactin (PRL) is a potent immunomodulator that exerts stimulatory effects on physiological responses of immune cells. In the present research we have investigated whether PRL, may influence nitric oxide (NO) and/or tumor necrosis factor-alpha (TNF-α) production in neutrophils obtained from inflammatory exudate of carrageenin-induced experimental pleurisy in the rat. In this acute model of inflammation the role of endogenous NO was evaluated using an inhibitor of NO-synthase, N(G)-nitro-L-arginine methyl ester (L-NAME). A treatment of animals with L-NAME (10 mg/kg s.c.) induced a reduction of volume and cell number of pleural exudate and a decrease of nitrite production (measured by the Griees reaction) by polymorphonuclear cells after 24 h of incubation, while D-NAME, the inactive isomer, was without effect. Neutrophils from ovine prolactin (oPRL) treated rats (5 mg/kg for 5 times s.c.) or from rats with a hyperprolactinaemia induced by pituitary gland graft produced higher amounts of NO both after 24 and 48 h of incubation. On the contrary, a clear reduction in the production of NO was found in neutrophils from rats treated with bromocriptine (BRC) (2 mg/kg s.c.), a dopamine D2-receptor agonist. TNF-α production (measured by MTT/cytotoxic assay) by neutrophils was markedly increased in PRL-treated or pituitary-grafted rats in comparison to controls, whereas BRC treatment reduced TNF-α production.
Meli, R., Mattace Raso, G., Gualillo, O., Pacilio, M., & Di Carlo, R. (1997). Prolactin modulation of nitric oxide and TNF-α production by peripheral neutrophils in rats. Life Sciences, 61(14), 1395–1403. https://doi.org/10.1016/S0024-3205(97)00685-1