An autoradiographic study on the occurrence of injected radiosulphate in the intestine

Reducing sulfur compounds of the colon impair colonocyte nutrition: implications for ulcerative colitis

BACKGROUND

Mercaptides (sodium hydrogen sulfide and sodium methanethiol) and mercapto-fatty acid (sodium mercaptoacetate) are reducing agents that help to maintain anaerobic conditions in the colonic lumen. The metabolic effect of these agents on n-butyrate and glucose oxidation in human colonocytes is unknown.

METHODS

Isolated human colonocytes were prepared from 31 colectomy specimens, and generation of oxidative metabolites from [1-14C]n-butyrate and [6-14C]glucose was measured in the presence and absence of reducing agents. Injury to cells was judged by diminished production of metabolites.

RESULTS

The injurious action of mercaptides at all sites of the colon was of the order of sodium hydrogen sulfide > methanethiol > mercaptoacetate. Significant inhibition of n-butyrate (< 0.005) but not glucose oxidation was observed with sodium hydrogen sulfide in the ascending colon, splenic flexure, and rectosigmoid region. Hydrogen sulfide more significantly inhibited fatty acid oxidation in the rectosigmoid than in the ascending colon (P < 0.02).

CONCLUSIONS

Metabolic effects of sodium hydrogen sulfide on butyrate oxidation along the length of the colon closely mirror metabolic abnormalities observed in active ulcerative colitis, and the increased production of sulfide in ulcerative colitis suggests that the action of mercaptides may be involved in the genesis of ulcerative colitis.

UPTAKE OF RADIOACTIVE SULPHUR BY VARIOUS TISSUES OF NORMAL AND CHOLESTEROL-FED RABBITS

The uptake of inorganic sulphur labelled with radioactive sulphate (S35) was studied in rabbits that had been fed a normal diet and rabbits that had been fed a similar diet supplemented by the addition of 1% of cholesterol for 4 months. Paper electrophoresis of alkaline extracts of cartilage, tendon, or aorta separated a peak of radioactivity that corresponded to a band that stained metachromatically with toluidine blue and that is assumed to be chondroitin sulphate. Characteristic peaks of radioactivity were found by electrophoresis of extracts of mucin-containing tissues of the gastrointestinal tract, indicating the location of sulphated mucus with a mobility different from that of chondroitin sulphate. No radioactive material was isolated from the tissues of cholesterol-fed animals that was not present in normal tissues. Highly significant over-all differences in specific activity of sulphur were found between various tissues in both normal and cholesterol-fed rabbits. A significant elevation of both specific activity and sulphur concentration was produced in the aorta as a result of cholesterol feeding.

UPTAKE OF RADIOACTIVE SULPHUR BY VARIOUS TISSUES OF NORMAL AND CHOLESTEROL-FED RABBITS

The uptake of inorganic sulphur labelled with radioactive sulphate (S35) was studied in rabbits that had been fed a normal diet and rabbits that had been fed a similar diet supplemented by the addition of 1% of cholesterol for 4 months. Paper electrophoresis of alkaline extracts of cartilage, tendon, or aorta separated a peak of radioactivity that corresponded to a band that stained metachromatically with toluidine blue and that is assumed to be chondroitin sulphate. Characteristic peaks of radioactivity were found by electrophoresis of extracts of mucin-containing tissues of the gastrointestinal tract, indicating the location of sulphated mucus with a mobility different from that of chondroitin sulphate. No radioactive material was isolated from the tissues of cholesterol-fed animals that was not present in normal tissues. Highly significant over-all differences in specific activity of sulphur were found between various tissues in both normal and cholesterol-fed rabbits. A significant elevation of both specific activity and sulphur concentration was produced in the aorta as a result of cholesterol feeding.

Turnover of S35-sulfate in the mucosa of the gastrointestinal tract of rats as seen in autoradiograms

Segments of the gastrointestinal tract removed from rats after intervals of time following injection of S(35)-sulfate were fixed in aqueous formalin and then washed in water. Contact and coated autoradiograms were prepared. The suggestion made by others that more of the labelled sulfate is fixed by the mucosa than by the underlying coats of the gastrointestinal tract is confirmed. In addition it was found that the isotope is fixed to a greater extent in the lower intestine than in the middle or upper portions of it. Coated autoradiograms revealed that 6 hours after administration of S(35)-sulfate more of the label was present in the goblet cells lying deep in the crypts of the mucosa than in those adjacent to the intestinal lumen. By the 24th hour the concentration of the isotope was strikingly higher and more uniform from cell to cell. The mucus in the intestinal lumen was also highly radioactive. At the end of 48 hours very little of the sulfur-35 remained in the intestinal wall or could be made out in the mucus of the lumen: the autoradiographic reaction was faint and diffuse as contrasted with the punctiform and intense reaction given by the specimens removed at the end of shorter intervals of time.