Involvement of opioid receptors in Met-enkephalin modulation of blast-transformation of mouse splenocytes.

The influence of Met-enkephalin on mitogenic stimulation of mouse splenocytes was investigated. Met-enkephalin (ME) was shown to suppress proliferation induced by Concanavalin A and activate proliferation induced by Staphylococcus enterotoxin A. Both effects were revealed at low (down to 10(-14) M) concentration of pentapeptide. Naloxone reversed ME influence on cell activation. The number of receptors for naloxone was shown to increase up to 2.5-fold during mitogenic activation. The difference in expression of various types of opioid receptors at mitogenic stimulation was demonstrated by ligand displacement experiments.