EFFECTS OF TRIBUTYLTIN BN CA2-URCHIN EGGS( HOMEOSTASIS AND MECHANISMSCONTROLLING CELL CYCLING IN SEA)

Tributyltin (TBT) is one of the widespread organotins in the marine en vironment: we have investigated its cellular targets in the eggs of th e marine invertebrate sea urchin Paracentrotus lividus. TBT was used a t concentrations ranging from 10(-9) to 10(-4) M. The lipophilic chara cter of TBT makes that the magnitude of the effects varied according t o the concentration of egg used. Concentrations of TBT being without e ffect on egg fertilisation inhibited first and second cleavage in a do se-dependent manner. Concentrations of TBT which block egg cleavage di d not alter egg membrane permeabilities to Ca2+ and Na+. TBT inhibited intracellular ATP-driven sequestration of Ca2+ into reticular compart ment but did not provoke Ca2+ leakage from these compartment. Blockade of eggs cleavage by TBT is accompanied by an inhibition of protein sy nthesis (S-35-methionine incorporation) and DNA synthesis (H-3-thymidi ne incorporation). Protein phosphorylation (P-32 incorporation) and hi stone HZ kinase activity were inhibited when cell cycling was arrested by organotin. Results are discussed in terms of concentration of TBT per egg protein in order to compare the particular sensitivity of the numerous cellular process affected by TBT. (C) 1997 Elsevier Science B .V.