Reduction of cell density dependent antigenic properties of intracellular Ca(2+)-regulating membranes by isoflurane in human endothelial cells.

An established cell line of human umbilical vein endothelial cells displays a pronounced shift in the distribution of intracellular Ca(2+)-regulating membranes as the cells grow towards confluence. In sparsely populated cultures a linearly oriented punctate pattern of vesicle-like structures is observed similar to the distribution found in many other eucaryotic cells. As the cell population increases, the membranes condense around the nucleus. In completely confluent cultures when the cells cease to proliferate, the antigen is no longer detectable by immunofluorescence; its absence is confirmed by Western blotting experiments. Double-labeling with antitubulin or phalloidin shows that the distribution of microtubules is not related to the distribution of the Ca(2+)-regulating membranes whereas the actin fibers are superimposable onto the linearly oriented punctate vesicle-like structures. If proliferating cells are treated with the volatile anesthetic isoflurane, the Ca(2+)-regulating membranes can no longer be detected with the antibody; however, in Western blots the antigen is still present. Staining is restored after the removal of isoflurane. Such a temporary disappearance of the immunocytochemical staining might be explained by a transient oxidation and subsequent configuration change of the antigen, rendering the epitope inaccessible to the antibody, since a treatment with low concentrations of NaBH4 of cells exposed to isoflurane restores the access of the antigen to the antibody.     

Xenon induces metaphase arrest in rat astrocytes.

The use of xenon as an almost ideal anesthetic with very little side effects is gaining clinical acceptance, yet its effects on the cellular level are still unclear. It affects intracellular Ca2+-homeostasis but up to now no cellular event or Ca2+-signaling system has been described to be specifically sensitive to xenon. Here we report for the first time a specific effect of xenon on astroglial cells not found with another volatile anesthetic, isoflurane, nor with helium nor with N2: treatment of primary astroglial cells from embryonic rat brain with xenon induces, apart from a slight retardation of the cell cycle, a block at metaphase. Upon removal of xenon cells arrested at metaphase complete their mitosis normally. Even under continuous exposure to xenon, cells can be rescued from metaphase arrest by a small and transient increase in intracellular Ca2+; cells enter anaphase despite the presence of xenon and complete cell division, exhibiting normal rate of chromosome movement and normal chromosome separation. These results suggest that xenon interferes with some Ca2+-dependent regulatory system required for the metaphase-anaphase transition; taking into account its anesthetic effects, xenon may be also involved in the control of glia-mediated signaling transfer.