title: Role of soluble zinc in ZnO nanoparticle cytotoxicity in Daphnia magna: A morphological approach.
abstract: The role of soluble zinc has been determined in Daphnia magna by a morphological approach, integrating a previous paper in which the ultrastructural damages to gut epithelial cells have been studied after ZnO nanoparticles exposure. In the present paper, the toxicity and morphological effects of soluble zinc from ZnSO4 have been determined in a 48-h acute exposure test. Daphnids have been exposed to six nominal zinc concentrations (0.075, 0.15, 0.3, 0.6, 1.2, and 2.4mg Zn/L) and then fixed for microscopic analyses. Data from the acute toxicity tests gave an EC50 value of 0.99mg/L and showed that no immobilization appeared up to 0.3mg Zn/L. Ultrastructural analyses of samples from the two highest concentrations showed large vacuolar structures, swelling of mitochondria, multilamellar bodies, and a great number of autophagy vacuoles. These findings have been compared to those from our previous study, and similarities and/or differences discussed. Based on the overall results it can be concluded that dissolved zinc ions played a key role in ZnO nanoparticle toxicity and that the morphological approach is an extremely useful tool for comparing toxicological effects as well. A possible common toxic mechanism of soluble zinc and ZnO nanoparticles was also proposed.
authors.affiliation: Department of Life Sciences, Università degli Studi di Milano, Via G. Celoria, 26, I-20133 Milan, Italy. Electronic address: renato.bacchetta@unimi.it.
authors.forename: Renato
authors.initials: R
authors.lastname: Bacchetta
authors.affiliation: Department of Life Sciences, Università degli Studi di Milano, Via G. Celoria, 26, I-20133 Milan, Italy.
authors.forename: Barbara
authors.initials: B
authors.lastname: Maran
authors.affiliation: CNR - Istituto di Scienze e Tecnologie Molecolari, Via C. Golgi, 19, I-20133 Milan, Italy.
authors.forename: Marcello
authors.initials: M
authors.lastname: Marelli
authors.affiliation: Department of Life Sciences, Università degli Studi di Milano, Via G. Celoria, 26, I-20133 Milan, Italy.
authors.forename: Nadia
authors.initials: N
authors.lastname: Santo
authors.affiliation: Department of Life Sciences, Università degli Studi di Milano, Via G. Celoria, 26, I-20133 Milan, Italy.
authors.forename: Paolo
authors.initials: P
authors.lastname: Tremolada
mesh_terms: D000818:Animals; D003621:Daphnia / Q000187:drug effects; D020895:Enterocytes / Q000187:drug effects / Q000473:pathology / Q000648:ultrastructure; D007413:Intestinal Mucosa / Q000187:drug effects / Q000473:pathology / Q000648:ultrastructure; D053768:Metal Nanoparticles / Q000633:toxicity*; D046529:Microscopy, Electron, Transmission; D023382:Toxicity Tests, Acute; D014874:Water Pollutants, Chemical / Q000633:toxicity*; D015034:Zinc Oxide / Q000633:toxicity*
chemical_list: D014874:Water Pollutants, Chemical; D015034:Zinc Oxide
keywords: Daphnia magna; Ionic zinc; TEM; Toxicity; Zinc oxide