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 Ca²⁺-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.