Adrenergic receptors regulate macrophage secretion

Macrophages have been shown to possess both alpha 2 and beta 2-adrenergic receptors which appear to antagonize each other. The ability of these two kinds of receptors to mediate macrophage secretion was tested, using alpha- and beta-antagonists, idazoxan and propranolol. Both antagonists could inhibit hydrogen peroxide and superoxide secretion, although the timing of the inhibition is different. However, only idazoxan has the ability to reduce nitrite accumulation, while propranolol fails to affect macrophage production. In addition, sodium nitrite was able to inhibit hydrogen peroxide and superoxide secretion, and hydrogen peroxide could reduce nitrite accumulation, suggesting that a negative cross-feedback mechanism exists.