Induction of heme oxygenase by hemin in cultured pig alveolar macrophages

Abstract

Heme oxygenase was induced in cultured pig alveolar macrophages by several inducers, such as heterologous rat erythrocytes, hemoglobin, hemin particles, and hemin solution, and hemin solution was found to be the most effective in inducing the enzyme. Under the standard conditions, where 1.5×108 alveolar macrophages were incubated with 60 nmol of hemin (final concentration in the medium, 3 μM), there was an initial lag phase of about 1 h and then the heme oxygenase activity increased almost linearly for about 5 h. The maximum activity attained was about 20-fold higher than the control values before the induction or in the cells incubated without hemin. Actinomycin D prevented the increase in heme oxygenase activity when added at the start of incubation, but when the drug was added after the induction had commenced, the heme oxygenase activity continued to increase for about 3 h after the addition of actinomycin D. The addition of cycloheximide at any time during incubation resulted in an immediate cessation of induction. Neither cobalt chloride nor cobalt-protoporphyrin induced heme oxygenase activity appreciably in the alveolar macrophage system. Also, hydrocortisone, insulin, dibutyryl cyclic AMP, theophylline, isoproterenol, and cyclic GMP had no remarkable effect on the heme oxygenase induction by hemin in cultured pig alveolar macrophages.