| Popis: |
The effects of halothane on the spatial and temporal dynamics of intracellular Ca^ concentration in single cultured smooth muscle cells of the rat aorta were studied by digital imaging microscopy using Ca＾ indicator fura-2. Changes in intracellular［Ca＾］were expressed as the ratios of fluorescence intensity at 500 nm excited by 340 nm and 380 nm. Halothane （0.5, 1.0, 2.0vol. %） itself had no detectable basal ［Ca＾］ changes in these cells. Arginine-vasopressin （AVP; 10^M）, one of vasoconstrictor agonists which mobilize intracellular Ca＾ by inositol 1, 4, 5-trisphosphate-induced Ca＾ release mechanism, increased the nuclear ［Ca＾］ more than the cytosolic ［Ca＾］. The increases in the nuclear ［Ca＾］ induced by AVP were greatly reduced by pretreatment with caffeine and ryanodine which deplete the caffeine-ryanodine sensitive intracellular Ca＾ storage. Halothane （0.5, 1.0, 2.0%） greatly attenuated the increase in ［Ca＾］ in both the nuclear and cytosolic regions. Halothane （1.0, 2.0%） abolished the differential rise in ［Ca＾］in both regions in response to AVP. The times to the peak responses of ［Ca＾］ were significantly prolonged by halothane. The results suggest that nucleus and/or perinuclear region are important Ca＾ store sites in response to AVP, and also that the caffeine and ryanodine sensitive Ca＾ storage sites exist in the perinuclear region. The results further suggest that halothane affects arginine-vasopressin-induced ［Ca＾］ increase by an inhibition of inositol 1, 4, 5-trisphosphate production and/or by an inhibition of inositol 1, 4, 5-trisphosphate-induced Ca＾ release from intracellular Ca＾ storage sites. |
