Effects of alcohols on responses evoked by inositol trisphosphate in Xenopus oocytes.

Abstract

SUMMARY1. The effects of ethanol and other alcohols on inositol 1,4,5-trisphosphate (InsP3) signalling were studied in Xenopus oocytes by the use of flash photolysis of caged InsP3. Calcium liberation induced by InsP3 was monitored by voltage-clamp recording of Ca2+-activated membrane currents, and by fluorescence of the Ca2+ indicator Fluo-3.2. Membrane current and fluorescence Ca2+ signals evoked by light flashes giving small responses were initially potentiated by bath application of ethanol (80-400 mM). However, the responses subsequently declined while ethanol was present and were strongly reduced or suppressed when it was removed.3. These effects did not arise artifactually from changes in photolysis of caged InsP3, as similar results were seen with responses evoked by intracellular injections of InsP3. Also, the effects on the membrane current did not arise primarily through actions on the Ca2+-dependent Cl-channels, since currents evoked by intracellular injections of Ca2+ were little changed by ethanol 4. Ethanol reduced the threshold level of InsP3 required to cause Ca2+ liberation. Thus, potentiation was most prominent with small responses evoked by brief light flashes, whereas the predominant effect on larger responses was inhibitory.5. The facilitatory and inhibitory actions of ethanol persisted after removing extracellular Ca2+.6. Intracellular injections of ethanol produced an initial inhibition of InsP3 responses, followed, in some oocytes, by a potentiation.7. Methanol had little effect on InsP3 responses, whereas butanol and other longchain alcohols produced strong inhibition, but little or no potentiation.8. We conclude that extracellular application of ethanol produces a rapid potentiation of InsP3-mediated Ca2+ liberation, and a more slowly developing inhibition. The potentiation may arise through stimulation of InsP3 formation at the plasma mebrane, whereas the inhibition occurs more deeply in the cell. Both actions were evident at relatively low concentrations (a few tens of millimoles per litre), and might thus be important in the behavioural effects of ethanol intoxication.

Effect of genetic background and activating stimulus on the timing of meiotic cell cycle progression in parthenogenetically activated mouse oocytes

“…In mouse oocytes, ethanol has been frequently employed as an activating agent (Cuthbertson et al 1981, Cuthbertson 1983, Winston & Maro 1995. Ethanol activates oocytes by promoting the formation of inositol 1,4,5-trisphosphate (IP 3 ) at the plasma membrane and the influx of extracellular Ca 2þ (Ilyin & Parker 1992), causing a large, single rise in intracellular Ca 2þ concentration (Cuthbertson et al 1981). Strontium is another popular activating agent, currently used in mouse nuclear transfer protocols (Wakayama et al 1998).…”

Acetylcholine induces Ca 2+ oscillations via m3/m4 muscarinic receptors in the mouse oocyte

“…For sperm, PLCζ in sperm triggers Ca 2+ oscillations at fertilization in mouse eggs [38]. For EtOH, external application of EtOH reduces the threshold level of InsP 3 required for Ca 2+ release and potentiates InsP 3 -mediated Ca 2+ release, probably by stimulation of InsP 3 formation at the level of the membrane [19]. Ionomycin acts as ionophore and strongly enhances Ca 2+ influx across plasma membrane.…”

Factors inducing the activation of reconstructed oocytes of farm animals in somatic cloning procedures

“…Ethanol, by stimulating the production of 1,4,5-inositol triphosphate (IP 3 ) also activates a certain number of oocytes, initiating rapid and intense release of Ca 2+ from intracellular deposits (Ilyin and Parker, 1992). Ethanol as an activating agent is particularly effective with regard to ovine oocytes (Loi et al, 1998), but less useful for activating cattle and porcine oocytes.…”