Hydrocortisone induces lipocortin 1 production by peripheral blood mononuclear cells in vivo in man.

The development of a novel, sensitive enzyme-linked immunoassay (ELISA) for the detection of human lipocortin 1 [ I ] has enabled examination of the corticosteroid inducibility of this protein. Lipocortin 1 (molecular mass 37 kDa) has recently been the subject of intense investigation to substantiate early claims that it mediates the anti-inflammatory effects of corticosteroids by antagonising the activity o f phospholipase A,. Although it has clearly been shown to have phospholipase A, inhibitory activity in vitro [2, 31, it remains uncertain whether this is a direct enzyme inhibition or due to an interaction with substrate [4]. Recombinant lipocortin 1 has recently been shown to mimic the effect of corticosteroid on carrageenan-induced paw oedema in rats IS], but there is no direct evidence that the protein can be induced in vivo by corticosteroid in man, although the promoter region of the DNA sequence does possess potential corticosteroid receptor binding sites [6]. A bolus 100 mg intravenous dose of hydrocortisone was given to eight healthy male volunteers (median age 35 years) in an attempt to monitor changes in lipocortin 1 levels in peripheral blood leucocytes. Each experiment was begun at 13:OO h to correspond with the daily trough of endogenous circulating cortisol. Heparinized blood samples were taken before steroid administration and frequently over the course of the ensuing 240 min. As a control, an identical procedure was carried out on two subjects, the steroid infusion being replaced by placebo. Leucocytes were separated by flotation on a FicollHypaque M-85 [ 5 1% (w/v) meglumine diatrizoate, 26% (w/ v ) sodium diatrizoate gradient. Plasma was also collected and