2.7. Gastric Secretion in Pylorus-Ligated Rats

The free and total acidity, volume, and pH of the gastric juice were determined using the method of Shay and Gruenstein [26]. Twenty-six SD rats were randomly assigned to four groups: control (n = 9), omeprazole 20 mg/kg (n = 6), PCE 100 mg/kg (n = 6), and PCE 300 mg/kg (n = 5). After a 24 h fast, samples were administered by oral gavage at a volume of 10 mL/kg body weight; the control group received the vehicle (distilled water) at the same volume. After 30 min of sample administration, rats were anesthetized with 2% isoflurane in 70% nitrous oxide and 30% oxygen. A 2 cm midline incision was made below the xiphoid process, and then the pyloric portion of the stomach was slightly lifted out and ligated avoiding bleeding or blood vessel occlusion. The stomach of each rat was placed carefully back into the abdomen and the wound was sutured. After 4 h of pylorus ligation, rats were euthanized by cervical dislocation and the stomach was removed. The gastric juice was collected and centrifuged at 3000 rpm for 10 min. The volume and pH of gastric juice were measured using a measuring cylinder and a pH meter (Ultrabasic benchtop meters, Denver Instrument, Denver, CO, USA). Free acidity was quantified by titration with 0.05 N sodium hydroxide using phenolphthalein as an indicator. Total acidity was calculated as follows: