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 i n concentration of plasma motilin and serum bile acids is unknown. Met hods: 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 b iliary 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 emp tying were observed with a median (range) duration of 25 min (15-45 mi n). Each episode of gallbladder emptying was followed by a steep incre ase in plasma motilin, reaching a median value of 30 pmol/l (13-43 pmo l/l), corresponding to an increase of 18 pmol/l (4-33 pmol/l). The inc rease in plasma motilin started at the beginning of gallbladder emptyi ng, 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 cy cle. The serum concentration of bile acids also showed a cyclic variat ion 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, h owever. In the pooled data from all subjects, a significant correlatio n (p < 0.01) between the serum concentration of bile acids and plasma concentration of motilin was found. Conclusion: Gallbladder emptying w as followed by a steep increase in plasma motilin concentration, and i n cases of two or more emptying periods during the MMC cycle the conce ntration decreased in between. The shape of the serum bile acid profil e is dependent on the intestinal transport and absorption of bile acid s, and the significance of the cyclic variation in serum concentration of bile acids in relation to plasma motilin, gallbladder motility, an d MMC needs further investigation.