SULFIDE IMPAIRMENT OF SUBSTRATE OXIDATION IN RAT COLONOCYTES - A BIOCHEMICAL BASIS FOR ULCERATIVE-COLITIS

1. Isolated colonic epithelial cells of the rat were incubated for 40m in with [6-C-14]glucose and n-[1-C-14]butyrate in the presence of 0.1- 2.0 mmol/l NaHS, a concentration range found in the human colon. Metab olic products, (CO2)-C-14 acetoacetate, beta-hydroxybutyrate and lacta te, were measured and injury to cells was judged by diminished product ion of metabolites. 2. Oxidation of n-butyrate to CO2 and acetoacetate was reduced at 0.1 and 0.5 mmol/l NaHS, whereas glucose oxidation rem ained unimpaired. At 1.0-2.0 mmol/l NaHS, n-butyrate and glucose oxida tion were dose-dependently reduced at the same rate. 3. To bypass shor t-chain acyl-CoA dehydrogenase activity necessary for butyrate oxidati on, ketogenesis from crotonate was measured in the presence of 1.0 mmo l/l NaHS. Suppression by sulphide of keto-genesis from crotonate (-10. 5+/-6.1%) compared with control conditions was not significant, wherea s suppression of ketogenesis from n-butyrate (-36.00+/-5.14%) was sign ificant (P = < 0.01). Inhibition of FAD-linked oxidation was more affe cted by NaHS than was NAD-linked oxidation. 4. L-Methionine (5.0 mmol/ l) significantly redressed the impaired beta-oxidation induced by NaHS . Methionine equally improved CO2 and ketone body production, suggesti ng a global reversal of the action of sulphide. 5. Sulphide-induced ox idative changes closely mirror the impairment of beta-oxidation observ ed in colonocytes of patients with ulcerative colitis. A hypothesis fo r the disease process of ulcerative colitis is that sulphides may form persulphides with butyryl-CoA, which would inhibit cellular short-cha in acyl-CoA dehydrogenase and beta-oxidation to induce an energy-defic iency state in colonocytes and mucosal inflammation.