TABLE 1

Effects of DTT on inhibition of TH caused by ONOO⁻ or NO₂ ± BH₄ TH was treated with reactive nitrogen species ± BH₄ as described under Materials and Methods. DTT (2 mM) was added immediately before treatment and remained in the samples throughout exposure conditions. In other experiments, DTT was added immediately after treatment and samples were incubated at room temperature for 30 min before assays for TH catalytic activity were carried out. Data are reported as percentage of control TH activity and represent mean ± S.E.M. of four separate experiments carried out in duplicate.

		DTT
Treatment	No DTT	Before Treatment	After Treatment
	%	%
Control	100	97 ± 5	94 ± 6
ONOO⁻	54 ± 2^a	97 ± 5^b	56 ± 3^a
ONOO⁻ + BH₄ (50 μM)	56 ± 6^a	78 ± 3^b	78 ± 5^b
ONOO⁻ + BH₄ (100 μM)	58 ± 5^a	81 ± 7^b	76 ± 7^b
NO₂	58 ± 4^a	97 ± 6^b	62 ± 5^a
NO₂ + BH₄ (50 μM)	72 ± 4^a	94 ± 3^b	83 ± 4^b
NO₂ + BH₄ (100 μM)	68 ± 4^a	95 ± 4^b	86 ± 6^b

↵ a Significantly different from control, P < 0.05 using Bonferroni's test.
↵ b Significantly different from respective no-DTT group, P < 0.05 using Bonferroni's test.