AIM:To investigate experimentally the effects of methionineenkephalin on signal transduction of mouse myeloma NS-1cells.METHODS:The antigen determinate of delta opioidreceptor was designed in this lab and the polypeptidefragment of antigen determinate with 12 amino acidsresidues was synthesized.Monoclonal antibody against thispeptide fragment was prepared.Proliferation of Mouse NS-1 cells treated with methionine enkephalin of 1×10~(-6)mol·L~(-1)was observed.The activities of protein kinase A(PKA)andprotein kinase C(PKC)were measured and thereby themechanism of effect of methionine enkephalin was postulated.RESULTS:The results demonstrated that methionineenkephalin could enhance the proliferation of NS-1 cells andthe effect of methionine enkephalin could be particularlyblocked by monoclonal antibody.The activity of PKA wasincreased in both cytosol and cell membrane.With referenceto PKC,the intracellular activity of PKC in NS-1 cells waselevated at 1×10~(-7)mol·L~(-1)and then declined gradually asthe concentration of methionine enkephalin was raised.Theeffects of methionine enkephalin might be reversed by bothnaloxone and monoclonal antibody.CONCLUSION:Coupled with the findings,it in-dicates thatthe signal transduction systems via PKA and PKC are involvedin the effects of methionine enkephalin by binding with thetraditional opioid receptors,and therefore resulting in differentbiological effects. AIM: To investigate experimentally the effects of methionine enkephalin on signal transduction of mouse myeloma NS-1 cells. METHODS: The antigen determinate of delta opioid receptor was designed in this lab and the polypeptide fragment of antigen determinate with 12 amino acids residues was synthesized. Monoclonal antibody against this peptide fragment was prepared. Proliferation of Mouse NS-1 cells treated with methionine enkephalin of 1 × 10 -6 mol·L -1 was observed. These activities of protein kinase A (PKA) and protein kinase C (PKC) were measured and thereby themechanism of effect of methionine enkephalin was postulated .RESULTS: The results of that methionineenkephalin could enhance the proliferation of NS-1 cells and the effect of methionine enkephalin could be particularly blocked by monoclonal antibody. The activity of PKA wasincreased in both cytosol and cell membrane.With referenceto PKC, the intracellular activity of PKC in NS-1 cells waselevated at 1 × 10 ~ (-7) mol·L -1 and then decline d gradually asthe concentration of methionine enkephalin was raised. effects of methionine enkephalin might been reversed by bothnaloxone and monoclonal antibody. CONCLUSION: Coupled with the findings, it in-dicates that the signal transduction systems via PKA and PKC are involved in the effects of methionine enkephalin by binding with thetraditional opioid receptors, and therefore resulting in differentbiological effects.