Thimerosal causes calcium oscillations and sensitizes calcium‐induced calcium release in unfertilized hamster eggs

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Abstract
Calcium‐induced‐calcium‐release (CICR) was assayed in unfertilized golden hamster eggs by injecting Ca2+ and monitoring Ca2+‐dependent hyper‐polarizing responses (HRs) and Ca2+‐sensitive fluo‐3 fluorescence. Incubating eggs in the sulfhydryl reagent thimerosal caused [Ca2+]1 oscillations as monitored by Ca2+‐dependent HRs and decreased approximately 10‐fold the Ca2+ injection current required to generate an HR and cause a large intracellular Ca2+ increase. Thimerosal also enhanced the sensitivity of eggs to Ca2+ injection in a calcium‐free medium. The effects of thimerosal on CICR were prevented by dithiothreitol and were not mimicked by injecting inositol 1,4,5‐triphosphate. The data suggest that thimerosal may be an alternative agent for studying CICR in caffeine‐insensitive cells.