The aim of this study was to assess the influence of five amino-amide local anesthetic agents on the production of oxygen metabolites in the human polymorphonuclear leukocyte (PMNL), both intra- and extracellularly. Ropivacaine, a new long-acting amino-amide local anaesthetic agent, bupivacaine, lidocaine, mepivacaine and prilocaine in concentrations 1-5 micrograms.ml-1 up to 500-1000 micrograms.ml-1 were compared to an untreated control. PMNLs were isolated from heparinized blood (healthy adult volunteers). Cells were incubated with the various local anaesthetics (37 degrees C, 30 min), then placed in a Biolumat (luminol-amplified chemiluminescence) and stimulated by formyl-methionyl-leucyl-phenylalanine (FMLP), phorbol myristate acetate (PMA) or ionomycin. Horseradish peroxidase (HRP) was added to discriminate between an intra- or extracellular response. In general, a decrease in chemiluminescence-response was seen with higher concentrations (500-1000 micrograms.ml-1) of the various local anaesthetics. Lidocaine showed a decrease even at lower concentrations. A marked increase in intracellular response for prilocaine 1000 micrograms.ml-1 (3894 mumol.l-1) accompanied by a reduction in extracellular response, using FMLP +/- HRP as a stimuli, was noted. Ropivacaine 1000 micrograms.ml-1 (3216 mumol-l-1) showed a decrease both intra- and extracellularly that was similar to, and even somewhat more pronounced than lidocaine 1000 micrograms.ml-1 (3692 mumol.l-1), when using PMA with or without HRP as the stimuli.