Acute ethanol effects on cell volume regulation.

In this work, the effects of ethanol on cellular osmoregulation were studied in isolated proximal renal tubules of Carassius auratus (goldfish). In hypotonic solutions the tubule cells swell rapidly (osmometric phase) and subsequently shrink towards isotonic volumes (volume regulatory decrease phase, VRD). The osmometric phase depends on the water permeability of the cell membrane and the magnitude of the osmotic gradient. The VRD phase is complex and is a function of activation of osmotic transporters with net KCl efflux followed by osmotically, obligated water. At 7, 10, and 12 mM ethanol, the membrane water permeability and osmotic ionic effluxes were increased. At higher ethanol concentrations (14 and 28 mM), the osmometric phase was moderately inhibited and VRD was abolished. The stimulatory effects of ethanol (7, 10, and 12 mM) on cellular osmoregulation are probably due to enhanced membrane fluidity (water permeability) and increased membrane calcium release (activation of KCl efflux). Inhibitory effects of ethanol (14 and 28 mM) on cell volume control are due to a combined decrement in water and KCl effluxes. This dose-related inhibition is likely due to incorporation of the amphipathic ethanol molecules with decreased hydrophobicity of the microenvironment of channels and transporters owing to displacement of structural lipids. In this system the threshold for osmoregulatory inhibition is between 12 and 14 mM.