INHIBITION AND STIMULATION OF ENZYMATIC-ACTIVITIES OF HUMAN FIBROBLASTS BY CORROSION PRODUCTS AND METAL-SALTS

Fibroblasts from normal human skin were cultured for a period of 21 da ys in the absence or in the presence of metal ions. The effects of sta inless steel (SS) corrosion products were compared to the effects of i ron, chromium and nickel ions used either separately (Fe, Or, or Ni so lutions) or combined (Fe+Cr+Ni solution). At several periods of time ( 4, 7, 14 and 21 days) the cell cultures were analysed for the followin g parameters: (a) metal ion accumulation by atomic absorption spectrom etry; (b) cell morphology and viability by the neutral red assay; (c) cell proliferation by DNA assessment, and enzyme activity by both (d) MTT reduction and (e) acid phosphatase activity. Results showed that S S-corrosion products and the corresponding metal ions combined at the same concentrations, Fe+Cr+Ni solution, had opposite effects on fibrob last cultures. In fact, SS-corrosion products caused no apparent effec ts on cell morphology nor on cell proliferation whereas Fe+Cr+Ni solut ion stimulated-both neutral red uptake and cell proliferation. The enz ymatic assays showed that SS-corrosion products caused inhibition of b oth MTT reduction and acid phosphatase activity in contrast to Fe+Cr+N i solution which stimulated their activity. Furthermore, in all biolog ical parameters studied, a strong association was observed between the effects of Fe+Cr+Ni solution and Cr alone, suggesting that Cr was the metal ion mostly involved in the stimulatory effects of the combined solution.