HIGH NITRIC-OXIDE SYNTHASE ACTIVITY IN ENDOTHELIAL-CELLS IN ULCERATIVE-COLITIS

Endothelial nitric oxide (NO) synthase, a unique NO synthase (NOS) iso form that is expressed constitutively by the vascular endothelium both in vivo and in vitro, is believed to be essential to systemic and/or local vascular integrity. NOS expression by endothelial cells may indi cate vascular activation. We successfully established a simple method for the culture of microvascular endothelial cells from a small amount of tissue and investigated ulcerative colitis (UC), in which conditio n vascular factors have not been studied extensively. We cultured endo thelial cells from the mesenteries of surgical patients with UC and as sayed NOS activity by reduced nicotinamide adenine dinucleotide phosph ate (NADPH)-diaphorase histochemistry. Strong NOS activity was demonst rated in the cells from all UC patients (5/5), whereas no activity was detected in the cells from human umbilical veins and the mesenteries of colon cancer patients (0/10 and 0/5, respectively). This strong NOS activity was not diminished by incubation with a high concentration o f glucocorticoid, suggesting that it was constitutive. These results i ndicate a close relationship of vascular activation (high NOS activity ) with the pathogenesis of UC.