INVITRO MODULATORY EFFECTS OF ENDOGENOUS OPIOID-PEPTIDES AND THYMOSINON MITOGEN-INDUCED BLAST-TRANSFORMATION

The present study investigates the in vitro effect of the endogenous o pioid peptides (EOP) beta-endorphin (beta-end) and Met-enkephalin (Met -enk) on the proliferation of resting and activated Balb/c mouse splee n cells, and the interactions between these two peptides and a thymic factor (thymosin fraction 5, TF5). Beta-end as well as Met-enk enhance d the proliferative eresponse of resting spleen cells to a statistical ly significant (P< 0.01) degree. However, these two EOPs showed an ant agonistic effect on T and B cell mitogens (Concanavalin A and lipopoly saccharide) respectively. Furthermore, the potentiating effects of bet a-end and Met-enk at various concentrations (10(-6), 10(-7) and 10(-8) M) were not blocked by a treatment with a 10, 100 or 1000 fold molar excess of naloxone. The mitotic effects of beta-end and Met-enk on mur ine spleen cells were blocked by 10 mug/ml of TF5. These data suggeste d that (i) EOP modulation may be mediated by a nonopiate but beta-end and Met-enk specific mechanism and that (ii) there was an antagonistic effect by TF5 on these EOPs. The physiological significance of these results may provide a link between the immune and neuroendocrine syste ms.