Possible involvement of eicosanoids in the zymosan and arachidonic-acid-induced oxygen uptake, glycogenolysis and Ca2+ mobilization in the perfused rat liver.

Abstract

Exposure of perfused rat livers to zymosan, arachidonic acid and phenylephrine, but not to latex particles, induces pronounced oxygen uptake, glycogenolysis and Ca2+ mobilization. The oxygen uptake induced by arachidonic acid and by zymosan remains elevated even after the agents have been removed. NaN3 was found to be much more effective in inhibiting the oxygen uptake induced by phenylephrine than that induced by zymosan or arachidonic acid. Glucose release induced by zymosan and by arachidonic acid reaches a maximum after about 2 min and then declines very rapidly even while the agents are still being infused. In contrast, glucose release induced by phenylephrine remains elevated for the duration of the infusion. Ca2+ fluxes induced by arachidonic acid are similar to those induced by phenylephrine in that efflux occurs when the agent is administered and influx occurs only when the agent is removed. This contrasts to the Ca2+ flux changes induced by zymosan where both Ca2+ efflux and Ca2+ influx occur even while zymosan is still being infused. Glucose release induced by zymosan is inhibited by bromophenacylbromide and nordihydroguaiaretic acid, but not by indomethacin. Indomethacin, however inhibits the arachidonic-acid-induced glucose release which is also inhibited by nordihydroguaiaretic acid but not by bromophenacylbromide. Indomethacin inhibits also the arachidonic-acid-induced Ca2+ flux changes whereas the zymosan- and the phenylephrine-induced Ca2+ flux changes are not inhibited by the cyclooxygenase inhibitor. The data presented in this paper suggest that in the perfused rat liver the zymosan-induced glycogenolysis, as well as the Ca2+ flux changes and glycogenolysis induced by arachidonic acid, are mediated by eicosanoids.