Effects ofcalcium andpHon themucosal damage produced bydeoxycholic acid intheratcolon

SUMMARY A single passperfusion system was usedinanaesthetised, restrained ratstoexamine theeffect ofchanging thecomposition oftheperfusion fluid on thedamage caused tothecolonic epithelium bydeoxycholic acid. Damagetothecolonic surface was monitored withlight microscopy, transmission andscanning electron microscopy andwithmeasurementsof deoxyribonucleic acid andcarbohydrate intheperfusate. Newscoring techniques formonitoring alterations insurface epithelium oflight microscopy sections were used. Thedamaging effect of 5mM deoxycholic acid tothecolonic epithelium isinhibited bylowering thepHoftheperfusion fluid from7-9to5*5, orbyincreasing thecalcium concentration from 0 to4mM.Thisinhibition is showntobebecause ofa decreased amountofbile acidinsolution. Thusitisnotthetotal concentration ofdeoxycholic acid inthecolon that isresponsible forthecolonic damage, butthe concentration insolution. Although extrapolation tothehumansituation mustbemadewith caution, theconcentration ofbile acidinsolution inthefaecal watermay bemore relevant to colonic mucosal damagethantotal bileacidconcentration.