Dual effects of n-alcohols on fluid secretion from guinea pig pancreatic ducts

Abstract

Ethanol strongly augments secretin-stimulated, but not acetylcholine (ACh)-stimulated, fluid secretion from pancreatic duct cells. To understand its mechanism of action, we examined the effect of short-chain n-alcohols on fluid secretion and intracellular Ca(2+) concentration ([Ca(2+)](i)) in guinea pig pancreatic ducts. Fluid secretion was measured by monitoring the luminal volume of isolated interlobular ducts. [Ca(2+)](i) was estimated using fura-2 microfluorometry. Methanol and ethanol at 0.3-10 mM concentrations significantly augmented fluid secretion and induced a transient elevation of [Ca(2+)](i) in secretin- or dibutyryl adenosine 3',5'-cyclic monophosphate (DBcAMP)-stimulated ducts. However, they failed to affect fluid secretion and [Ca(2+)](i) in unstimulated and ACh-stimulated ducts. In contrast, propanol and butanol at 0.3-10 mM concentrations significantly reduced fluid secretion and decreased [Ca(2+)](i) in unstimulated ducts and in ducts stimulated with secretin, DBcAMP, or ACh. Both stimulatory and inhibitory effects of n-alcohols completely disappeared after their removal from the perfusate. Propanol and butanol inhibited the plateau phase, but not the initial peak, of [Ca(2+)](i) response to ACh as well as the [Ca(2+)](i) elevation induced by thapsigargin, suggesting that they inhibit Ca(2+) influx. Removal of extracellular Ca(2+) reduced [Ca(2+)](i) in duct cells and completely abolished secretin-stimulated fluid secretion. In conclusion, there is a distinct cutoff point between ethanol (C2) and propanol (C3) in their effects on fluid secretion and [Ca(2+)](i) in duct cells. Short-chain n-alcohols appear to affect pancreatic ductal fluid secretion by activating or inhibiting the plasma membrane Ca(2+) channel.