Comparison of NiSO4 and NiCl2 as sensitizers in the guinea pig.

Nickel sulfate (NiSO4) and nickel chloride (NiCl2) were evaluated as sensitizers in the Guinea Pig Maximization Test (GPMT). The highest concentrations of NiSO4 or NiCl2 used as an intradermal challenge (0.25 and 0.5%) yielded responses that were significantly different (p less than 0.05) between exposed and control guinea pigs at 24 h, and the highest concentration (0.5%) yielded significant differences (p less than 0.05) at 48 h. The responses at the 0.125% NiSO4 challenge site were significantly greater (p less than 0.05) than for controls at both 24 and 48 h. Using the lymphocyte transformation test (LTT), the stimulation indices for the NiSO4- and NiCl2- exposed guinea pigs were nearly identical; however, the difference between exposed and control groups was greater for NiSO4 than for NiCl2. The results of both intradermal skin challenge and lymphocyte transformation indicated that NiSO4 may be preferable to NiCl2 in the GPMT. Because the skin test yielded statistically significant results while LTT did not, the skin test may be of more value when using these sensitizers in the GPMT.