Superoxide Generation by Neonatal and Adult Rabbit Alveolar Macrophages

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Abstract
We compared the abilities of alveolar macrophages (AM) from neonatal and adult rabbits to generate and release superoxide (O2) after exposure to soluble and particulate stimuli. Basal rates of O2 release, 0.1–0.2 nmol/106AM/10 min, were modestly increased by exposing AM to phorbol myristate acetate, (dihy-dro)cytochalasin B, or cytochalasin C. Opsonized zymosan was a more effective stimulus, and maximal rates of O2 release were observed when AM were stimulated by a combination of opsonized zymosan and one of the aforementioned cytochalasins. Cytochalasins D and E were each potent activators of O2″ production by AM in the absence of additional stimuli. Adult AM released 24.8 ± 6.0, 20.4 ±4.4, and 33.5 ± 6.4 nmol O2- /106AM/10 min after stimulation by cytochalasin D, cytochalasin E, and dihydrocytochalasin B plus opsonized zymosan, respectively. Following exposure to the same stimuli, AM from 1, 3- and 7-day-old rabbits released O2″ at rates that ranged from 45 to 75% of corresponding adult values. The discrepancy between O2 production by neonatal and adult AM was accentuated when comparisons were restricted to AM recovered from bacteriologically sterile respiratory tracts. Our data show the O2 generating capacity of neonatal AM to be substantially less than that of the adult AM. Immaturity of this response could predispose neonates to pulmonary infection.