Gallbladder responses to modified sham feeding: effects of the composition of a meal.

Changes in gallbladder contraction and plasma cholecystokinin release were studied following modified sham feeding of 3 different isocaloric meals rich in either fat, protein or carbohydrates in healthy volunteers, and results were compared with those following real feeding of comparable meals. In contrast to carbohydrate-rich meals (8 +/- 19 ml/120 min), fat- (-412 +/- 46 ml/120 min) and protein-rich meals (-352 +/- 42 ml/120 min) reduced integrated gallbladder volume (P < 0.05) in response to modified sham feeding. Plasma cholecystokinin levels were not significantly influenced by modified sham feeding of fat, protein or carbohydrates. Real feeding of a carbohydrate-rich meal also failed to significantly reduce gallbladder volume and to stimulate cholecystokinin release (-45 +/- 40 ml/120 min and 51 +/- 11 pmol/120 min, respectively), while real feeding of both fat- and protein-rich meals distinctly reduced gallbladder volume (-679 +/- 76 and -564 +/- 53 ml/120 min, respectively; P < 0.05) and increased cholecystokinin release (651 +/- 72 and 504 +/- 43 pmol/120 min, respectively; P < 0.05). This study demonstrates that gallbladder contraction during the cephalic phase of meal stimulation is dependent on the fat, protein and carbohydrate percentages of a meal, and is activated by different mechanisms than the intestinal phase of a meal.