Mechanism of arachidonic acid-induced Ca2+ mobilization in liver nuclei.

Arachidonic acid treatment in isolated liver nuclei resulted in a rapid and transient increase of Ca2+ concentration in the nucleoplasm which was monitored with the Ca(2+)-sensitive dye fura-2 dextran. This effect was associated with a decrease of Ca2+ concentration in the nuclear envelope as measured with fura-2 AM. Our results indicate that arachidonic acid causes a Ca2+ release from the nuclear envelope to the nucleoplasm similar to that evoked by inositol trisphosphate (IP3). The arachidonic acid-induced Ca2+ mobilization in the nucleus was not due to the metabolites of arachidonic acid. Experiments performed in the presence of ATP and Ca2+ indicate that arachidonic acid-induced Ca2+ mobilization in the nucleus takes place in a non ATP-dependent way. Taken together, these results suggest that arachidonic acid may contribute to the regulation of nuclear Ca2+ mobilization.