Background: The cysteinyl leukotrienes (cys-LTs) are proinfl ammatory mediators synthesized through the 5-lipoxygenase pathway of arachidonic acid metabolism. Cys-LTs exert their biological action by binding two types of G-protein-coupled seven transmembrane receptors, CYSLTR1 and CYSLTR2. The contribution of the cys-LT receptors to bronchial asthma has been established by the therapeutic effi cacy of biosynthetic inhibitors and selective CYSLTR1 blockers.

Objective: The present study was designed to analyse two different polymorphisms 927T>C CYSLTR1 and -444A>C LTC4S, and to determine whether there is an association between these polymorphisms and the asthma phenotype in a Spanish population.

Methods: Both single nucleotide polymorphisms (SNPs) were analysed in 208 individuals (130 asthmatic subjects and 78 controls). A standardized history, physical examination, skin prick tests and lung function measurement were taken from all patients. Genotypes were determined by direct sequencing after polymerase chain reaction (PCR) amplification.

Results: In the group of male patients, the C allele of 927T > C CYSLTR1 was more common among patients with asthma than controls. No association was detected between the - 444A> C LTC4S polymorphism and the asthma phenotype. The combination of 927T CYSLTR1 and - 444A LTC4S was less common in male patients with asthma than in controls (Fisher´s P-value = . 039; Monte Carlo P-value (after 104 simulations) = .045 and the combination of 927C CYSLTR1 and - 444A LTC4S was slightly more frequent in patients with asthma. No differences were observed in the female group.

Conclusions: The results suggest a certain trend of associations that could help to explain some controversial results in association studies of these genes from the leukotriene pathway, when considered individually. Further studies are needed to confi rm such an association.

Key words: Asthma. Gene. CYSLT. LTC4. Leukotrienes. Polymorphism.