Triggering by ATP of product release by mucous granules of the land slug Ariolimax columbianus

Abstract

The body wall of the pulmonate land slug Ariolimax columbianus secretes mucus packaged in granules bounded by two closely adjacent membranes. Newly secreted granules rupture in the presence of ATP (approximately 1 microM). This response is apparently mediated by an ATP receptor and is lost by granules held in osmotically balanced saline solutions with relatively low [K+] or [Cl-], but is retained for long periods in solutions with high [K+] and [Cl-]. Rupture by ATP is blocked by indomethacin, furosemide, nigericin, or verapamil, implicating in the ATP-rupturing process a cyclooxygenase product of arachidonic acid as well as activation of K(+)-Cl- transport and efflux of Ca2+ through activated channels according to a proposed electrical potential (proton) gradient. Mechanical stress, exposure to cold (e.g., 1 h at 0 degree C), and pertussis toxin also cause rupture that is blocked by the pharmacological agents that block ATP action. The results suggest that a single basic mechanism causes rupture of the granules, releasing mucins that form the mucous layer protecting the body wall.