Corticosteroid increases gastrointestinal luminal proteolysis in suckling rats

Although stress during the perinatal period may influence a number of enzymes in the gastrointestinal tract, the resulting effects on digestive processes are not completely understood. In suckling rats, corticosteroid administration increases levels of proteases in gastric mucosa and pancreas, but previous studies of unstimulated luminal fluid proteolytic activity suggest no effect. To re-evaluate this phenomenon, we injected suckling rats with cortisone acetate (5 mg/100 g body weight) subcutaneously daily on days 9-11 followed by sacrifice on day 12; littermates served as controls. Luminal fluid from stomach and small intestine was analyzed for proteolytic activity by a sensitive assay in which incubation in vitro with 125I-bovine casein was followed by measurement of radioactivity soluble in trichloroacetic acid. Cortisone acetate produced significant increases in luminal proteolytic activity in all gastrointestinal segments with the most dramatic effect observed in the ileum; this segment showed a more than 10-fold enhancement of proteolysis with steroid treatment. Analysis of acid-precipitable reaction products by electrophoresis in polyacrylamide gels containing sodium dodecyl sulfate also revealed enhancement of casein degradation by luminal fluid in all segments from steroid-treated animals. We conclude that corticosteroid increases luminal proteolysis in the gastrointestinal tract of the suckling rat. This phenomenon may have implications for steroid-induced premature closure to macromolecular absorption and protein digestive capacity during the perinatal period.