title: Regulatory volume decrease in nematocytes isolated from acontia of Aiptasia diaphana.
abstract: Regulatory volume decrease (RVD) and the mechanisms of its regulation were investigated in microbasic mastigophore nematocytes isolated from the acontia of Aiptasia diaphana (Coelenterates, Cnidaria), a marine species that can be exposed to considerable changes in osmotic pressure. Exposure of isolated cells to a 35% hypoosmotic shock lead to the expected osmotic swelling followed by a rapid RVD. RVD was blocked if Ca2+ influx was prevented either by applying a Ca2+-free medium or by treating the cells with Gd3+. Furthermore, the calmodulin action inhibitor trifluoperazine (TFP), prevented RVD and also caused a larger swelling than that induced by preventing Ca2+ influx. Treatment of nematocytes with quinine completely blocked the RVD. Such an effect was prevented by gramicidine. A partial inhibition of RVD was caused by treatment with 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS). It is concluded that: i) the nematocytes regulate volume under hypoosmotic shock; ii) the regulatory mechanisms consist mainly in increased conductance to K+, and consequently, of Cl-, and, to a lesser extent, in H+/K+-Cl-/HCO3- exchange, and iii) the ionic fluxes are triggered by increased [Ca2+]i with the possible involvement of calmodulin.
authors.affiliation: Institute of General Physiology, University of Messina, Italy. glaspada@imeuniv.unime.it
authors.forename: G
authors.initials: G
authors.lastname: La Spada
authors.forename: T
authors.initials: T
authors.lastname: Biundo
authors.forename: R
authors.initials: R
authors.lastname: Nardella
authors.forename: S
authors.initials: S
authors.lastname: Meli
mesh_terms: D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D000818:Animals; D048429:Cell Size / Q000187:drug effects; D009997:Osmotic Pressure; D011803:Quinine / Q000494:pharmacology; D012615:Sea Anemones / Q000166:cytology*
chemical_list: D011803:Quinine; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid