The effect of soybean trypsin inhibitor on acute gastric mucosal lesions, produced by haemorrhagic shock and intra-gastric hydrochloric acid instillation, was studied in the pylorus-ligated rat. Five minutes following intra-gastric injection of 0.1 N HCl, and immediately prior to the onset of haemorrhagic shock, soybean trypsin inhibitor (STI) 15 mg/kg was given intravenously. Control rats received an equal volume of 0.9% saline. Rats were subjected to haemorrhagic shock for 20 minutes and then the shed blood was reinfused. Following a 20 minute recovery period, rats were sacrificed and their stomachs removed. The gastric specimens were opened and scored in a blinded fashion for mucosal ulceration. The percentage area ulceration in the control group was 13.7 ± 3.6 compared to 3.3 ± 1.1 in the STI group (p < 0.02). In the control group, transgastric potential difference (PD -ve mVolts) fell from 33.9 ± 0.9 to 6.6 ± 2.2 mV (p < 0.002) during shock. In the STI group, PD fell from 35.2 ± 1.7 to 20.3 ± 4.7 (p < 0.005). The fall in potential difference was significantly greater in the control group compared to the STI group (p < 0.02). In this model, STI administration results in significant protection of gastric mucosa during haemorrhagic shock, possibly by inhibiting generation of oxygen-free radicals.
