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Calcium mobilization and its desensitization induced by endothelins and sarafotoxin in human astrocytoma cells (1321N1): comparison of histamine-induced calcium mobilization.

Intracellular free Ca2+ concentration ([Ca2+]i) was monitored in monolayer of 1321 N1 astrocytoma cells by using a fluorescent Ca2+ indicator fura-2. Endothelin-1 (ET-1), endothelin-2 (ET-2), and sarafotoxin Sb6 (SRTX) increased [Ca2+]i from 56 +/- 6 nM to 360 +/- 82, 120 +/- 51, 143 +/- 29 nM, respectively, immediately after their addition to the perfusate with maximum response of more than 0.1 microM of peptides. Endothelin-3 (less than 1 microM) did not affect [Ca2+]i. The increase in [Ca2+]i in response to either ET-1, ET-2, or SRTX could be almost completely inhibited by pretreating cells with ET-1 or ET-2. The homologous desensitization of [Ca2+]i induced by ETs and SRTX is in good agreement with their affinity toward an ETA receptors. The responses in [Ca2+]i by ETs and SRTX were not affected in the desensitized state induced by the pretreatment of histamine in the presence of extracellular Ca2+. However, the response in [Ca2+]i by ETs and SRTX were reduced in the desensitized state induced by pretreatment of histamine in the absence of extracellular Ca2+. These results indicate that depletion of the intracellular Ca2+ stores is responsible for the heterologous desensitization between ETs and histamine.

Calcium↗

Study of fractionation and potential mobility of metal from the Guadalquivir estuary: changes in mobility with time and influence of the aznalcollar mining spill.

This study analyzed the evolution of metal levels in surface sediments from the Guadalquivir estuary between 1997 and 2002 and assessed the impact of the April 1998 Aznalcollar tailings dam failure and subsequent cleanup on metal concentrations in surface sediments. We also analyzed metal distribution with time in five chemical fractions of the surface sediments: exchangable, carbonate, reducible, oxidizable, and residual. This work showed that the April 1998 Aznalcollar tailings dam failure caused a considerable increase in the concentrations of Cd, Zn, Cu, and Pb in the surface sediments of the Guadalquivir estuary. It was also found there was a change in the distribution of Cd, Zn, Cu, and Pb between the chemical fractions of the sediment after the failure of the dam. There were increases in the percentages of Cd in the carbonate fraction, of Zn and Pb in the reducible fraction, and of Cu in the oxidizable fraction, whereas the percentages of these elements associated with the residual fraction decreased. In 1999, there was a decrease in the metal concentrations in the surface sediments from the Guadalquivir estuary, and by 2000 the chemical distribution and metal levels had returned to levels similar those before the dam failure.

Ecosystem↗