Nitric oxide synthase is increased following small intestinal transplantation in the rat

Transplantation of the small intestine is a neural model that could include extrinsic denervation, loss of intrinsic enteric neurons, or loss of intri nsic neural pathways. Nicotinamide adenine dinucleotide phosphate (NADPH) d iaphorase activity was measured in normal rat ileum, ileum 3 months after r esection of the jejunum, and ileum 3 months after isotransplantation of the ileum. The distribution of NADPH diaphorase activity and immunoreactive ne uronal nitric oxide synthase were examined. Nicotinamide adenine dinucleoti de phosphate diaphorase activity was increased in transplanted ileum (16.5 +/- 3.5 mU/mg protein) compared to normal controls (6.6 +/- 0.7) and resect ion controls (6.8 +/- 0.6) (P < 0.05, ANOVA). Histologically, NADPH diaphor ase activity and immunoreactive nitric oxide synthase appeared increased wi thin nerve cell bodies following transplantation. These findings may repres ent an adaptive response of the enteric nervous system to extrinsic denerva tion. Loss of intrinsic neural pathways was not supported as a mechanism. ( C) 1999 Elsevier Science S.A. All rights reserved.