Adrenergic receptors on monocytes modulate complement component synthesis.

The addition of adrenaline, noradrenaline or phenylephrine, but not isoprenaline to monocyte cultures enhanced synthesis of the second complement component (C2). This effect was abrogated by the concomitant addition of the receptor antagonist, phentolamine, but not the beta receptor antagonist propranolol. Thus the receptor involved is an alpha adrenergic receptor. Further studies showed that the receptor was of the alpha 1 subclass as prazosin inhibited the action of adrenergic agonists. Pulse label studies using 3H-amino acids showed that the enhancement of synthesis of eight complement components (C2, C3, C4, C5, factor B, properdin, beta 1H and C3b inactivator) and total protein synthesis were also increased. The possible mechanisms underlying these changes are discussed.