Interaction between nitric oxide and cyclooxygenase pathways.

Nitric oxide (NO) is an inorganic free radical gas, of formula -N=O. The demonstration in 1987 that the endothelium-derived relaxing factor (EDRF) 1 was NO-3 and the subsequent discovery of L-arginine as the amino acid precursor for the formation of NO 4,5 have disclosed a novel area of interdisciplinary research. The relevance of the L-arginine:NO pathway was primarily documented by the identification of NO as a key mediator in the regulation of vascular tone, 6 neurotransmission z8 and host defence mechanisms? Moreover, the discovery of a growing number of NO-regulated functions (e.g. memory, sensory processing, endocrine system, reproduction, airway resistance) suggests that virtually every mammalian cell is actually or potentially under the control of NO) . In this light, it is not surprising that prostaglandin (PG) biosynthesis appears to be modulated by the L-arginine:NO pathway, Interestingly, other findings suggest that prostanoids may regulate NO production in a variety of cell types. This brief review will summarize the recent information dealing with the 'cross-talk' occurring between the Larginine:NO and cyclooxygenase pathways, particularly at the level of the inflammatory response.