EFFECT OF IN-VITRO AND IN-VIVO ADMINISTRATION OF DEXAMETHASONE ON RATMACROPHAGE FUNCTIONS - COMPARISON BETWEEN ALVEOLAR AND PERITONEAL-MACROPHAGES

Resident alveolar macrophages (AMs) and peritoneal macrophages (PMs), though they originate from common precursor cells, differ morphologica lly and functionally. The two types of macrophages residing in differe nt tissues may respond differently to glucocorticoids. In the present study, we compared the effects of a synthetic glucocorticoid, dexameth asone (Dex), on rat AMs and PMs with regard to their phagocytic activi ty and tumour necrosis factor-alpha (TNF-alpha) releasability. In vitr o exposure of the macrophages to Dex caused the depression of phagocyt ic activity of AMs but not of PMs. In contrast, TNF-alpha releasabilit y was depressed in the both types of macrophages, and no difference wa s found between AMs and PMs in their susceptibility to TNF-alpha regul ation by Dex. When Dex was administered subcutaneously in to rats, pha gocytic activity was severely depressed in AMs but not in PMs. On the other hand, TNF-alpha releasability was depressed both in AMs and PMs by the in vivo Dex administration. The depression in PMs, however, was transitory and less severe that that in AMs. These results suggest th at alveolar macrophages and peritoneal macrophages differ intrinsicall y in responses to glucocorticoid, and that the cell location and the c ell's microenvironment can also modulate the effects of glucocorticoid on macrophage functions.