Apoptosis induction in vivo and fate of apoptotic material in the colon ofthe guinea pig

Short-chain fatty acids (SCFA) in particular butyrate are regarded as an en ergy source acting in beneficial, protective manner on the colonic mucosa. Previous investigations showed that the colonic mucosa bathed in Ussing cha mber with a solution lacking butyrate induced massive apoptosis of epitheli al cells. The apoptotic material (bodies and cells) was shed at the mucosa surface. In the present study we aimed to investigate the effects caused in vivo on the colonic mucosa by the absence of butyrate. For this purpose th e colon of guinea pigs was perfused in situ with solutions either containin g or lacking butyrate. The results show that within 2h of perfusion without butyrate a large amount of epithelial cells underwent apoptosis as in the in vitro experiments, However, apoptotic material instead to be extruded at the epithelial surface accumulates into the intercellular spaces from whic h it becomes removed by an unusual high number of macrophages. These, engor ged with phagocytozed material, he assembled in a layer below the epitheliu m. Similar alterations have not been observed after perfusion in the presen ce of butyrate, The results suggest that this SCFA may protect the colonic mucosa in that it prevents apoptosis. The alterations occurring during 2h o f its absence allow to assume that a protracted butyrate deprivation may le ad to a breakdown of the integrity of the mucosa thus influencing different ly the activity of the macrophages.