The function of granulocytes and alveolar macrophages following a single dose of endotoxin in rabbits. Effects of methylprednisolone

Abstract

It is a generally held opinion that steroids attenuate the activation of phagocytes. However, this statement has its limitations; in rabbit endotoxemia, for instance, steroids enhance the procoagulant activity of monocytes. The present study aimed to investigate the release of toxic oxygen metabolites (TOM) from granulocytes and alveolar macrophages 24 h after endotoxin injection in rabbits, and the effect of concomitant injection of methylprednisolone (MP). Release of TOM was assessed by peak chemiluminescence (CLP). Expression of thromboplastin activity by alveolar macrophages was determined as well, employing a recognized method for assessment of activity. In terms of mean +/- s.e.mean, endotoxin increased granulocyte count from a baseline value of 1.8 +/- 0.2 X 10(6) cells/ml to 3.7 +/- 1 X 10(6) cells/ml, which increased further to 9.8 +/- 2.5 X 10(6) cells/ml following administration of MP. Whereas endotoxin given alone caused no significant change in granulocyte CLP, additional administration of MP increased CLP from 1723 +/- 389 to 16610 +/- 8428 counts. On the other hand, MP attenuated an endotoxin-induced increase in both CLP and thromboplastin activity of alveolar macrophages. Thus, MP appears to have a proinflammatory effect on circulating granulocytes in rabbit endotoxemia, simultaneously depressing the function of stationary macrophages. This may suggest an injurious effect of MP in rabbit endotoxemia.