Irradiation increases superoxide dismutase in rat intestinal smooth muscle.

We investigated whether X-irradiation could induce the enzyme superoxide dismutase (SOD) in intestinal muscle. Groups of rats received abdominal irradiation and the time course and dose response for SOD activity determined. Jejunal smooth muscle homogenates were analyzed for the activities of copper/zinc (CuZn) and manganese (Mn) SOD activity and for a mitochondrial marker enzyme, citrate synthase. A progressive rise in Mn SOD activity occurred at 20, 46, and 72 h after 1500 R. No significant changes in Cu-Zn SOD activity occurred at any time after 1500 R. At 20 h after 250 R of X-irradiation, Mn SOD activity increased but no further increase occurred at higher irradiation exposures. At the same time, CuZn SOD activity at 20 h after irradiation was greater than controls only at an exposure of 1000 R (p less than 0.05). Using Western blotting, we were able to clearly demonstrate an increase in immunoreactive Mn SOD protein in muscle samples 20 h after 1500 R. The rise in Mn SOD is not simply due to increase in mitochondrial numbers or increase in all mitochondrial enzyme activities because activity of the mitochondrial marker enzyme citrate synthase was decreased after X-irradiation. Transmission electron microscopic studies demonstrated damage to mitochondria after a dose of 3000 R. The data yield evidence that free radicals play a role in irradiation-induced intestinal smooth muscle injury.

Chronic intestinal pseudoobstruction in young children.

We studied 8 young children (4 boys and 4 girls) with chronic intestinal pseudoobstruction. Intestinal pseudoobstruction, recurrent urinary tract infections, and dysuria occurred between the ages of a few weeks to 5 yr old. All had marked dilatation of the entire gastrointestinal tract distal to the esophagus, and megacystis. Conventional pathologic examinations of the full-thickness specimens of the gastrointestinal tract were normal in 5 and abnormal in 2 patients. The abnormalities included increased fibrosis and lipofuscin pigment in the smooth muscle cells. Myenteric plexus examination, using the Smith's method in 2 patients, was normal. Biopsy specimens from urinary bladders examined in 3 patients revealed separation of individual smooth muscle cells by collagen fibers. Intestinal manometric studies performed in 3 patients showed only weak and infrequent contractions during fasting and after feeding. Severe and extensive dysfunction of the gastrointestinal and urinary tracts with relatively normal histologic appearance are typical for these children.