INVOLVEMENT OF CALCIUM IN MACROPHAGE LEUKOTRIENE RELEASE DURING EXPERIMENTAL CIRRHOSIS

The aim of the present study was to assess the mechanism of 5-lipoxyge nase metabolites (LT) secretion by peritoneal macrophages in rats with CC14 induced cirrhosis, After stimulation with calcium ionophore A231 87 or opsonized zymosan, [H-3] arachidonic acid labeled macrophages fr om cirrhotic rats presented a significantly greater secretion of LT th an macrophages from healthy controls, In addition, the phorbol ester T PA (protein kinase C activator) increased LT production only in macrop hages from cirrhotic animals and not in controls, Although Ca2+ is tho ught to be involved in 5-lipoxygenase activation, the role of Ca2+ in LT production was studied. The use of a Ca2+-free medium as well as th e addition of TMB-8 (an inhibitor of intra-cellular Ca2+ movements and of plasma membrane Ca2+ fluxes) resulted in a fall in LT production g reater for macrophages from cirrhotic animals than for controls. The m easurement of cytosolic Ca2+ concentration by cytofluorimetry showed t hat Fluo-3 loaded macrophages from cirrhotic rats had a greater cytoso lic Ca2+ concentration than macrophages from control animals both in b asal conditions and after A23187 stimulation, Study of Ca-45(2+) uptak e suggest, that extra cellular Ca2+ is implicated in the elevated cyto solic Ca2+ observed in macrophages from cirrhotic animals as compared to healthy controls, The greater Ca2+ concentration observed in macrop hages from cirrhotic rats was not related to a difference in phospholi pase C activation because inositol phosphate production did not differ between macrophages from healthy and cirrhotic animals, Taken togethe r these results suggest that as compared to healthy animals, the great er LT production during cirrhosis could be dependent upon a difference in B-lipoxygenase activation related to a rise in cytosolic Ca2+ conc entration independently of inositol phosphates generation.