INCREASES IN PLASMA MOTILIN FOLLOW EACH EPISODE OF GALLBLADDER EMPTYING DURING THE INTERDIGESTIVE PERIOD, AND CHANGES IN SERUM BILE-ACID CONCENTRATION CORRELATE TO PLASMA MOTILIN

Background: The relationship between each single period of gallbladder emptying during the migrating motor complex (MMC) cycle and changes in concentration of plasma motilin and serum bile acids is unknown. Methods: The variations in the concentration of plasma motilin and serum bile acids in relation to interdigestive gallbladder motility and the MMCs was studied in nine healthy male volunteers. A method combining biliary scintigraphy (Tc-99m-labelled dimethyl-iminodiacetic acid) and continuous pressure recording from the antroduodenal region was used. Results: During 9 MMC cycles a total of 15 episodes of gallbladder emptying were observed with a median (range) duration of 25 min (15-45 min). Each episode of gallbladder emptying was followed by a steep increase in plasma motilin, reaching a median value of 30 pmol/l (13-43 pmol/l), corresponding to an increase of 18 pmol/l (4-33 pmol/l). The increase in plasma motilin started at the beginning of gallbladder emptying, but the peak value was not reached until a median of 20 min (10-45 min) later. Low plasma motilin concentrations were found between the emptying periods in cases with two or more emptyings during the MMC cycle. The serum concentration of bile acids also showed a cyclic variation in relation to gallbladder motility. During periods of gallbladder emptying serum bile acid concentration had a median value of 1.78 mu mol/l, as compared with a median value of 1.17 mu mol/l during periods of gallbladder filling. This difference did not reach significance, however. In the pooled data from all subjects, a significant correlation (p < 0.01) between the serum concentration of bile acids and plasma concentration of motilin was found. Conclusion: Gallbladder emptying was followed by a steep increase in plasma motilin concentration, and in cases of two or more emptying periods during the MMC cycle the concentration decreased in between. The shape of the serum bile acid profile is dependent on the intestinal transport and absorption of bile acids, and the significance of the cyclic variation in serum concentration of bile acids in relation to plasma motilin, gallbladder motility, and MMC needs further investigation.