Hydrocortisone (HC) substantially inhibits adenosine-5′-triphosphate (ATP)γS-induced CXCL8 and CXCL1 production by human microvascular endothelial cell line-1 (HMEC-1) while penicillin (PCN) has only a small inhibitory effect on CXCL1 and CXCL8 release. HMEC-1 cell cultures were treated with tetracycline (TCN), HC or PCN and then stimulated with ATPγS (100 μm) or left unstimulated. Supernatants were collected 24 h later and analysed for CXCL8 (a) and CXCL1 (b) content. (a) CXCL8: P = 0.006 for 10 μg/ml of TCN, P < 0.0001 for 100 μg/ml of TCN, P < 0.001 for 10 μg/ml of HC, P < 0.0001 for 100 μg/ml of HC, P = 0.09 for 10 μg/ml of PCN and P = 0.020 for 100 μg/ml of PCN. (b) CXCL1: P = 0.005 for 10 μg/ml of TCN, P < 0.0001 for 100 μg/ml of TCN, P = 0.58 for 10 μg/ml of HC, P < 0.0001 for 100 μg/ml of HC, P = 0.004 for 10 μg/ml of PCN and P = 0.012 for 100 μg/ml of PCN.