The effect of acute inflammatory lung injury on the respiratory burst and protein kinase C activity of rat pulmonary alveolar macrophages

After induction of acute inflammatory lung injury in rats, unstimulated and zymosan-stimulated pulmonary alveolar macrophages (PAM) in suspension consumed significantly greater amounts of oxygen than did comparably stimulated PAM from noninjured lungs. Although oxygen consumption by PAM from injured lungs after stimulation with phorbol 12-myristate 13-acetate (PMA) was increased, it was not significantly different from that of PMA-stimulated PAM fron noninjured lungs. Despite the enhanced oxygen consumption, PAM from injured lungs in suspension did not secrete more superoxide (O2-) than did comparably stimulated PAM from noninjured lungs. It has been suggested that the respiratory burst in human polymorphonuclear leukocytes (PMN) and monocytes is dependent on the translocation of protein kinase C (PKC). We established that PKC was present in rat PAM and that acute lung injury did not alter total PKC activity or the subcellular distribution of the enzyme. Similarly, stimulation of PAM from noninjured lungs (zymosan, PMA) or injured lungs (zymosan) did not result in translocation of PKC activity, despite an enhanced oxidative burst. These results indicate that although PKC activity was present in PAM, translocation of PKC activity was not necessary for the respiratory burst.