Objective:To explore the inhibitive effects of exogenous nitric oxide on the proliferation of in vitro cultured human keloid fibroblasts.Methods:Fibroblasts was isolated from fresh pathological scar tissue and cultured.Fibroblasts were distributed in five groups.Fibroblasts in control group A was cultured without SNP;in experiment group B～D

SNP was used in the concentration of 100、200、300 μmol/L each;in experiment group E

Fibroblasts was cultured with 200 μmol/L SNP and 10 μmol/L methylene blue.After 24h

Griess and MTT were used to detect the concentration of NO and cell vigor.Results:The release of NO increased along with the enhancement of the concentration of SNP.The amount of living cells in experiment groups decreased compared with the controls as shown by MTT tes(tP<0.05)

but in experiment group E

the amount of living cells was increased than group C(P<0.05).Immunocytochemical detection shows:SNP treatment decreased the expression of collagen Ⅰ

and expression of collagen Ⅰ increased after treated by Methylene blue.Conclusion:Exogenous nitric oxide inhibits the proliferation of of in vitro cultured human keloid fibroblasts

and these may be result in NO-GC-cGMP path way.