Coordination of gastric and gallbladder emptying after ingestion of a regular meal

The relationship of gallbladder emptying and refilling to gastric emptying of solids, gastrointestinal transit time, and human pancreatic polypeptide response was examined after ingestion of a standard breakfast (40% fat) in 12 healthy men and women. Gallbladder volume, emptying, and refilling was measured by real-time ultrasonography, and gastric emptying of solids was measured scintigraphically by the disappearance from the stomach of egg labeled with 99mTc-sulfur colloid. Gastrointestinal transit time was defined as the time of initial rise in breath hydrogen following ingestion of 10 g of lactulose. Serum human pancreatic polypeptide level was measured by radioimmunoassay. Gallbladder emptying was biphasic, initially 0.015 +/- 0.003 min-1 and later 0.005 +/- 0.001 min-1, and gallbladder volume remained small until refilling began at 249 +/- 67 min. Gallbladder refilling was 70% complete at 335 +/- 57 min. The slower rate of gallbladder emptying and tonic gallbladder contraction occurred during gastric emptying of solids. Gallbladder refilling began when approximately 13% of solids remained in the stomach. Serum human pancreatic polypeptide showed the expected biphasic response to the meal and returned to basal levels at approximately the time of initiation of gallbladder refilling. The gastrointestinal transit time of women was twice that of men (73.6 +/- 20.2 vs. 37.5 +/- 22.7, p = 0.025). No other sex-related differences were detected. We conclude that gastric emptying of the solid portion of a meal containing fat maintains tonic gallbladder contraction through continued release of humoral mediators from small bowel and pancreas. When gastric emptying nears completion, humoral stimulation ceases and the gallbladder refills. Human pancreatic polypeptide does not appear to be responsible for gallbladder refilling.