GLUTAMINE DEPRIVATION INDUCES APOPTOSIS IN INTESTINAL EPITHELIAL-CELLS

Background, Glutamine is the most abundant amino acid in the blood; an d its deprivation leads to gut mucosal atrophy. The small intestinal m ucosa is maintained by a balance between cell proliferation and cell d eath by apoptosis. We reported that glutamine is required for mitogen- stimulated proliferation in intestinal epithelial cells. We do not kno w whether glutamine regulates apoptosis in the gut. The purpose of thi s study is to determine whether glutamine deprivation induces apoptosi s in rat intestinal epithelial (RIE-1) cells and to compare the effect of glutamine starvation with that of methionine and cysteine (Met/Cys ) starvation. Methods. RIE-1 cells were deprived of either glutamine o r Met/Cys for 24 hours. Cell numbers were determined by cell counting and tetrazolium enzymatic assay. Apoptosis was quantified by Annexin a ssay and confirmed by DNA gel electrophoresis and Hoechst nuclear stai ning. Results. Deprivation of glutamine or Met/Cys resulted in decreas ed cell numbers, However; only the glutamine-deprived group showed sig nificant induction of apoptosis with increased Annexin V staining; DNA laddering, and nuclear condensation. Conclusions. This study provides biochemical and morphologic evidence that glutamine deprivation induc es apoptosis in rat intestinal epithelial cells. In contrast, Met/Cys starvation suppresses cell number without induction, of apoptosis. The se results suggest that glutamine serves as a specific survival factor in enterocytes.