Table 1

Effect of PABA on NAT1 activity in human cell lines

Cell Line	–PABA	+PABA	% Loss of NAT1 Activity
	nmol/min/mg protein	nmol/min/mg protein
THP-1 (confluent)^1-a	22.6 ± 0.6	12.1 ± 0.2^1-150	47 ± 7
THP-1 (exp. growth)	26.9 ± 0.2	24.3 ± 0.3	9 ± 4
MCF-7^1-b	7.3 ± 0.1	3.0 ± 0.1^1-150	59 ± 7
Jurkat^1-c	10.1 ± 0.01	5.6 ± 0.1^1-150	45 ± 4
CEM^1-d	14.8 ± 0.03	7.8 ± 0.4^1-150	47 ± 13

Cells were grown to confluence (except where indicated) in PABA-free BME medium and then cultured for a further 24 h in the absence or presence of 25 μM PABA. NAT1 activities were measured in cell cytosols and expressed as mean ± S.E. (n = 3).

↵1-a THP-1, human monocytic cell line.
↵1-b MCF-7, human breast carcinoma cell line.
↵1-c Jurkat, human lymphocytic cell line.
↵1-d CEM, human lymphoblastic leukemia cell line.
↵1-150 Significant differences (P < .05) from control (–PABA) values.