1-->3-Beta-Glucans, derived from the inner cell wall of yeasts and fungi, are commonly found in indoor air dust samples and have been implicated in organic dust toxic syndrome. In a previous study, we reported that 1-->3-Beta-glucan (zymosan A) induced acute pulmonary inflammation in rats. The present study investigates which form of 1-->3-Beta-glucans, particulate or soluble, is more potent in inducing pulmonary inflammation. Zymosan A was suspended with 0.25 N NaOH for 30 min, neutralized, dialyzed for 2 days against deionized water, and particulate and soluble fractions collected. Male Sprague-Dawley rats were exposed via intratracheal instillation to NaOH-soluble or NaOH-insoluble zymosan A (1.8 mg/ml, 0.26 ml). At 18 hrs post-exposure, various indicators of pulmonary response were monitored, including indicators of lung damage, such as serum albumin concentration and lactate dehydrogenase activity in acellular bronchoalveolar lavage fluid. Inflammation was characterized by an increase in lavageable polymorphonuclear leukocytes (PMN), pulmonary irritation (breathing frequency increase) and oxidant production (nitric oxide and chemiluminescence (CL)). Exposure to the particulate fraction of NaOH-treated zymosan caused a significant increase in all these indicators. In contrast, rats exposed to the NaOH-soluble fraction did not show significant increase for most of these indicators except for albumin, PMN and CL. However, these increases were significantly smaller than with exposure to NaOH-insoluble zymosan. Therefore, the results demonstrate that particulate zymosan A is more potent in inducing pulmonary inflammation and damage in rats than the soluble form of this Beta-glucan.
The Toxicologist. Society of Toxicology 41st Annual Meeting and ToxExpo, March 17-21, 2002, Nashville, Tennessee