Figure 3. Effects of lipopolysaccharide (LPS)-induced NO production on protein tyrosine phosphatase (PTP) activities in rabbit vascular smooth muscle cells (RVSMC). RVSMC were incubated for 24 h with LPS. A, Non-confluent, low-density RVSMC were exposed to LPS (10 ng/ml). The inducible NO synthase inhibitor aminoguanidine (AG, 400 µM) was added 30 min prior to the incubation with the endotoxin, as indicated. B, Concentration-dependent effects of LPS on RVSMC-associated PTP activities in multilayered cultures. After 24 h, cells were lysed and lysates had their protein concentration determined. Protein contents were matched (100 µg) and PTP activity in lysates was measured as described in Material and Methods. Results are reported as means ± SD of three independent experiments. *P<0.01 compared to medium and +P<0.05 compared to cells pretreated with AG (Student t-test).