Emptying of saline meals by the cat stomach as a function of pyloric resistance

The effect of the pylorus on the rate of gastric emptying and on the pattern of flow from the stomach to the duodenum was studied. Cat stomachs were filled with 50, 100, or 150 ml of 0.9 N saline, and intragastric pressure and gastric fluid output were monitored continuously. The tip of the collecting cannula was positioned either in the duodenum thus allowing the pylorus to close) or in the pyloric segment thus preventing the pylorus from interfering with gastric outflow). Initial experiments demonstrated that fluid output was similar for the cat stomach in situ and in vitro. Incremental output (i.e., the absolute volume emptied per collection period) increased with the meal size and was proportional to the fluid volume actually remaining in the stomach; fractional gastric output (i.e., the volume emptied as a percentage of the actual gastric volume) did not change with meal size. The half time for gastric emptying was greater with the collecting cannula positioned in the duodenum than in the pylorus (e.g., with the 100-ml meal, 154 vs. 46 s). With the cannula in the pylorus, gastric outflow was constant and ceased only when gastric emptying had terminated. With the cannula in the duodenum, outflow was pulsatile and ceased intermittently at gastric volumes that were subsequently emptied. We conclude that the cat pylorus renders the outlet of the stomach continent even to liquids; furthermore, the pylorus imparts a pulsatile pattern to flow of liquids from the stomach to the duodenum.