SummaryThis research investigated the effect of glutamine (Gln) depletion on leucocyte-dependent inflammatory events. Rats were treated intraperitoneally, 16 hr prior to the peak of every parameter evaluated, with either 0Á9% NaCl, methionine-sulphoximine (MSO, an inhibitor of endogenous Gln synthesis, 25 mg/kg) or with MSO + Gln (MSO as above plus Gln 3 g/kg in three doses). MSO-induced Gln depletion increased paw oedema induced both by carrageenan (Cg) and by Clostridium difficile toxin A (TxA) (66Á2% and 45Á5%, respectively; P < 0Á05). In dextran-injected animals, oedema and myeloperoxidase (MPO) activity were not modified by Gln depletion. In Cg-treated paws, Gln depletion increased MPO activity by 44% (P < 0Á05), interleukin-1b (IL-1b) and tumour necrosis factor-a (TNF-a) concentrations by 47% and 52%, respectively (P < 0Á05), and immunostaining for TNF-a in paw tissue. In TxA-injected paws, Gln depletion increased MPO activity (46%; P < 0Á05). Gln depletion increased Cg-and TxA-induced neutrophil migration to subcutaneous air pouches by 56% and 77% (P < 0Á05), respectively, but did not affect migration induced by N-formyl-methionyl-leucyl-phenylalanine (fMLP). Gln infusions reversed all the effects of MSO. Leucocyte counts did not differ between groups. Gln depletion potentiates acute inflammation, possibly by increasing neutrophil migration through resident cell activation and production of IL-1b and TNF-a. Gln supplementation reverses these effects and may be useful during inflammatory catabolic stress.