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Modulation of the agonist-specific cytosolic Ca 2+ o~cillatory pattern by thimerosal has been investigated in single pancreatic acinar cells using patch-clamp perforated whole-cell recording to measure the calcium-dependent chloride current (lcl(c~÷)). 1 gM thimerosal, which falls to evoke Ca 2+ oscillation alone, clearly changed the pattern of Ca 2+ oscillation from pulsatile spikes (evoked by low concentrations of activators) to sinusoidal or transient oscillations. The mimetic action of thimerosal was independent of extracellniar Ca 2+, was blocked by extracellular application of dithiothreitol or 10 mM caffeine, as well as by internal perfusion with heparin; but was unaffected by ruthenium red. We conclude that thimerosal modulates the agonist-specific cytosolic Ca 2+ oscillatory patterns mediated by sensitizing the InsP3-indnced Ca 2+ release.

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