THURSDAY, March 26 (HealthDay News) -- Variations in several genes can influence children's lung growth and function, as well as how vulnerable they are to secondhand smoke, say University of Southern California researchers.

"Many factors can affect lung function and growth, including genetic variation and environmental exposures such as tobacco smoke and air pollutants," study lead author Carrie Breton said in a USC news release.

"We wanted to determine whether specific gene variations would have measurable and predictable effects on lung function growth and susceptibility to environmental insults," she said. "We looked at a class of genes known to be involved in antioxidant defense, the glutathione-s transferase (GST) genes. Overall, we found that variation in several of the GST genes was important. This was particularly true for children of mothers who had smoked during pregnancy."

Breton and colleagues analyzed eight years' worth of lung function and genotyping data from more than 2,100 children. They identified three specific halotypes (patterns of genetic variation within genes) that had a significant effect on lung function. These halotypes were found in the genes GSTM2, GSTM3 and GSTM4.

The gene variants may not alter lung development, the researchers explained, but they may change the ability of the lungs to defend against damage caused by free radicals, such as those found in smoke.

"The GST genes are important to the detoxification of reactive oxygen species, including carcinogens and environmental exposures, such as cigarette smoke. We speculate that the patterns of genetic variation we investigated may alter this process, thereby reducing the lung's ability to detoxify harmful agents and causing a cascade of other events that promote inflammation, bronchial constriction, airway hyper-responsiveness and asthma-like symptoms," Breton said.

The study is in the first April issue of the American Journal of Respiratory and Critical Care Medicine.

"The next step would be to investigate how these genes interact with one another to jointly affect lung development," Breton said. "Future studies should also investigate the timing and quality of tobacco smoke exposure during pregnancy in combination with variation in these genes to further understand how they jointly affect fetal lung development."

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