Ethanol inhibits the motility of rabbit sphincter of Oddi in vitro

The role of the sphincter of Oddi (SO) in ethanol (ETOH)-induced pancreatitis is controversial. Our aim was to characterise the effect of ETOH on basal and stimulated SO motility.

SOs removed from white rabbits were placed in an organ bath (Krebs solution, pH7.4, 37 degrees). The effects of 2 mL/L, 4 mL/L, 6 mL/L and 8 mL/L of ETOH on the contractile responses of the sphincter were determined. SOs were stimulated with either 0.1 mumol/L carbachol, 1 mumol/L erythromycin or 0.1 mumol/L cholecystokinin (CCK).

ETOH at a dose of 4 mL/L significantly decreased the baseline contractile amplitude from 11.98+/-0.05 mN to 11.19+/-0.07 mN. However, no significant changes in the contractile frequency were observed. ETOH (0.6%) significantly decreased both the baseline amplitude and the frequency compared to the control group (10.50+/-0.01 mN, 12.13+/-0.10 mN and 3.53+/-0.13 c/min, 5.5+/-0.13 cycles(c)/min, respectively). Moreover, 0.8% of ETOH resulted in complete relaxation of the SO. Carbachol (0.1 micromol/L) or erythromycin (1 micromol/L) stimulated the baseline amplitudes (by 82% and 75%, respectively) and the contractile frequencies (by 150% and 106%, respectively). In the carbachol or erythromycin-stimulated groups 2-6 mL/L of ETOH significantly inhibited both the amplitude and the frequency. Interestingly, a 4-5 min administration of 0.6% ETOH suddenly and completely relaxed the SO. CCK (0.1 micromol/L) stimulated the baseline amplitude from 12.37+/-0.05 mN to 27.40+/-1.82 mN within 1.60+/-0.24 min. After this peak, the amplitude decreased to 17.17+/-0.22 mN and remained constant during the experiment. The frequency peaked at 12.8+/-0.2 c/min, after which the constant frequency was 9.43+/-0.24 c/min throughout the rest of the experiment. ETOH at a dose of 4 mL/L significantly decreased the amplitude from 16.13+/-0.23 mN to 14.93+/-0.19 mN. However, no significant changes in the contractile frequency were observed. ETOH at a dose of 6 mL/L inhibited both the amplitudes and the frequencies in the CCK-stimulated group, while 8 mL/L of ETOH completely relaxed the SO.

ETOH strongly inhibits the basal, carbachol, erythromycin, and CCK-stimulated rabbit SO motility. Therefore, it is possible that during alcohol-intake the relaxed SO opens the way for pancreatic fluid to flow out into the duodenum in rabbits. This relaxation of the SO may protect the pancreas against alcohol-induced damage.