Expression of NOS isoforms in human mast cell populations. nNOS: RT-PCR analysis of nNOS mRNA in HMC-1 (lane 1), KU812 (lane 2), skin MCs (lane 3), and LAD 2 cells (lane 4). Human brain RNA was used as a positive control (lane 5). iNOS: RT-PCR analysis of iNOS mRNA in HMC-1 (lane 1), KU812 (lane 2), skin MCs (lane 3), and LAD 2 cells (lane 4). Human brain RNA was used as a positive control (lane 5). eNOS: RT-PCR analysis of eNOS mRNA in HMC-1 (lane 1), KU812 (lane 2), skin MCs (lane 3), and LAD 2 cells (lane 4). Human endothelial cell RNA was used as a positive control (lane 5). The sizes of expected amplified products are indicated. Molecular weight markers (M) are indicated. Results are representative of at least 3 independent RNA isolations.