Lipase in Canine Gastric Juice

Abstract

Gastric lipase has been demonstrated in uncontaminated gastric juice (3, 4, 6) and within the gastric mucosa (1, 7) of man and various laboratory animals. In the present study, the effect of stimulation with histamine and Urecholine on secretion of lipase by canine Heidenhain pouches was determined. Materials and Methods. Collection of gastric juice. Two trained female mongrel dogs, weighing 19 and 21 kg, respectively, were equipped with chronic Heidenhain pouches. The pouches remained free of infection or exudation along the metal cannula. After collection of unstimulated gastric juice for 2 hr, saline with histamine (124 μg/kg/hr) or Urecholine (88 μg/kg/hr) was infused intravenously for 3 hr at a constant rate of 11.5 ml/hr. With each drug, three experiments per dog were performed. In two experiments, stimulated juice was pooled and collected at 30-min intervals (see experiments with 30-min samples). In one experiment, all collections of the second and third hour of stimulation were pooled (see experiments with pooled gastric juice). Gastric juice was collected in cooled containers, refrigerated immediately after collection, and incubated for determination of enzyme activity within 4 hr after collection. Determination of lipolysis. The rate of hydrolysis of trioctanoin in vitro was used as an estimate of the concentration of lipase in gastric juice. Octanoic acid was measured after incubation of 1 ml of gastric juice with 20 μl of trioctanoin. The pH of gastric juice was adjusted with 0.2 M citrate buffer (pH 2, 3, 4, or 5), phosphate buffer (pH 5, 6, 7, or 8), tris buffer (pH 8 or 9), or by titration with 0.2 M NaOH or HCl. To this mixture, trioctanoin was added (20 μ1/1 ml of gastric juice). Incubations were performed for 60 min in a shaking waterbath at a temperature of 37°. Due to the rapid shaking (150 shakes/min) the fat was kept in milky suspension.