A B S T R A C T The effect of corticosteroids on angiotensin converting enzyme was investigated in endothelial cell cultures and intact rat lung. Cultured endothelial cells from bovine aorta showed net production of angiotensin converting enzyme (ACE) over 2 d culture in serum-free medium. Dexamethasone (DM) increased cell ACE activity six-to sevenfold at 100 nM with a threshold effect at 0.3 nM. The effect of DM on ACE production was completely inhibited by actinomycin D or cycloheximide. Deoxycorticosterone (DOC) and aldosterone were markedly less active, with a threshold near 100 nM and significant (two to threefold) stimulation of ACE activity at 1 ,uM. In cells incubated in the presence of 10 nM DM, DOC (10 ,iM) significantly inhibited ACE production compared with 10 nM DM alone, suggesting that DOC is a partial agonist/partial antagonist in this enzyme system. Protein content of cells or medium was unchanged by steroids at all doses used.In vivo, adrenalectomized rats showed lower pulmonary ACE compared with intact controls, and when injected with DM (40 ,ug/d for 4 d) showed a significant (twofold, P < 0.002) increase in lung ACE over oil-injected, adrenalectomized controls; serum ACE did not change. Injection with DOC (40 jg/d) or aldosterone (10 jg/d) had no effect on lung or serum ACE. Over a range (0.6 to 2,000 jig) of concentrations of DM administered daily for 7 d, the dose-response curve of DM for induction of pulmonary ACE mirrored that for thymolysis; for both, half-maximal effects were seen at -6 jg DM/d, and plateau levels at 60 Ag/d.Received for publication 23 November 1981 and in revised form 18 May 1982. We conclude that glucocorticoids are potent inducers of ACE activity in endothelial cells in culture and in rat lung in vivo, and that the action of aldosterone and DOC reflects occupancy of glucocorticoid receptors. This effect may be of (patho)physiological relevance in regulating levels of ACE in local vascular beds, and thereby modulating local levels of the vasoactive peptides angiotensin II and bradykinin.

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1. Endothelial cells from bovine aortae were grown to confluence in tissue culture. The cells were subcultured and angiotensin converting enzyme (ACE) production was measured while the cells were maintained in serum-free medium for 4 days. 2. During this period, there was a ten-fold increase in ACE concentration in the medium whereas the cellular content of the enzyme remained constant at approximately 23% of the total enzyme produced. Cycloheximide (1 mumol/l) blocked production of ACE. 3. The enzyme liberated into the medium closely resembled ACE in the following respects: it cleaved the dipeptide histidyl-leucine from a synthetic tripeptide substrate, was markedly Cl- activated and inhibited by EDTA (1 mmol/l), SQ 14225 (1 mumol/l) or SQ 20881 (1 mumol/l). 4. Cells maintained in culture for up to ten passages have maintained morphology typical of endothelial cells and continue to produce ACE.

Normal human serum markedly stimulated aldosterone production from rat adrenal glomerulosa cells incubated in Krebs Ringer bicarbonate medium (KRBGA). The effect was dose-related. In [K+] 3.6 mM KRBGA medium, serum stimulated aldosterone output to higher levels than those produced by maximal doses of serotonin (5 HT), angiotensin II (All) or high [K+] (8.4 mM). Cells maximally stimulated by high [K+], 5 HT or All in KRBGA medium were further stimulated by serum. The angiotensin analogue, [Sar1, Ala8]-AII abolished the effect of All but not that of high [K+] or serum.Basal and ACTH-stimulated corticosterone outputs of rat fasciculata cells were not significantly affected by sera known to stimulate glomerulosa cells. Aldosterone stimulating activity of serum was dialysable and fully recovered in a serum ultrafiltrate. The serotonin blockers methysergide and metergoline abolished the aldosterone stimulating activity of serum but also depressed basal aldosterone output and methysergide reduced K+-stimulated output. Chymotrypsin digestion abolished the aldosterone stimulating activity of All but not that of serotonin or serum. 5 HT concentration of sera was measured and found to be near the threshold for aldosterone stimulation. Sodium loading and depletion of 4 normal subjects did not consistently modify the aldosterone stimulating activity of their sera. In a supplemented medium (RPMI 1640), basal and K+-stimulated aldosterone outputs were higher than in KRBGA medium. Under these conditions serum stimulated aldosterone output in normal [K+] medium but only marginally in high [K+] medium. In RPMI medium, serum did not further stimulate cells maximally stimulated with serotonin.Serum appears to stimulate aldosterone production from glomerulsoa cells by two different mechanisms: One is probably due to a serotonin-like substance. A separate effect of serum, seen only in KRBGA medium, is to enhance aldosterone output of glomerulosa cells maximally stimulated by K+, 5 HT or All.

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