Cholecystokinin octapeptide (CCK8)-stimulated amylase release in isolated rat pancreatic acini was inhibited over 30% by 600 mM ethanol. The configuration of the dose-response curve for CCK8, however, in the presence of ethanol was similar to that of the control. Amylase release elicited by maximal concentrations of CCK8 (300 pM) was inhibited by increasing concentrations of ethanol (0.3 to 1.3 M), and this inhibition was concentration dependent. In addition, the binding of [125I]CCK33 to specific membrane receptors on acini was inhibited by ethanol in a dose-dependent manner. A positive correlation between the inhibitory effects of ethanol on CCK binding and CCK-induced amylase release was observed. Furthermore, these inhibitory effects of ethanol were reversible. Basal amylase release, however, was increased 20-50% by ethanol between the concentrations of 0.3 and 1.3 M; higher concentrations caused a leakage of amylase from the acini both in the absence and presence of 300 pM CCK8. This is confirmed by 51Cr release from prelabeled acini which revealed no significant damage to acinar cell membrane between 0.3 and 1.6 M ethanol, but significant damage to acini at higher concentrations. These data suggest that the 600 mM ethanol-induced inhibition of CCK action in acini is due to reversible perturbation of the acinar cell membrane.