Consequences of prolonged inhalation of ozone on F344/N rats: collaborative studies. Part III: Effects on complex carbohydrates of lung connective tissue.
Glycosaminoglycans are constituents of proteoglycans, which are integral components of lung connective tissue. Glycosaminoglycans not only provide structural support to organs, but also influence extracellular matrix assembly, cell adhesion, and cell proliferation. Changes in the metabolism of glycosaminoglycans have been noted in several pulmonary diseases, for example, pulmonary fibrosis and emphysema. We studied quantitative and qualitative changes of glycosaminoglycans in the lungs of rats exposed to a range of ozone levels (0, 0.12, 0.5, 1.0 parts per million) for 20 months. Glycosaminoglycans were isolated from dry-defatted lung tissues through successive digestions by pronase, papain, and 2 M sodium hydroxide. The glycosaminoglycans then were fractionated into individual components using high-performance liquid chromatography. The concentration of total glycosaminoglycans in the tissues varied from 1.5 to 4.2 micrograms of uronate/mg of dry-defatted tissue. Although wide variations in total glycosaminoglycan concentrations exist among individual animals within each exposure group, regression analyses of data indicate a monotonic and statistically significant decrease of total glycosaminoglycans after ozone exposure (p = 0.02). Among individual glycosaminoglycans, hyaluronan, chondroitin 4-sulfate, and chondroitin 6-sulfate levels decreased significantly (p < 0.001, p < 0.05, and p < 0.01, respectively) in animals exposed to ozone when compared with control animals. Heparan sulfate concentration exhibited a significant (p < 0.05) trend toward increase with increasing doses of ozone, but the difference in heparan sulfate concentration between ozone-exposed animals and control animals was not significant. Gel filtration studies of glycosaminoglycans in pooled samples indicated that the molecular size of hyaluronan in animals exposed to ozone was lower than it was in control animals. We noted differences in heparan sulfate's chemical properties and affinity to antithrombin III in ozone-exposed animals and control animals. Although these studies do not provide the mechanism responsible for the observed changes in the lung glycosaminoglycans in ozone-exposed animals, the observations indicate that inhalation of ozone for 20 months affects normal cellular metabolism of proteoglycans, which may contribute to the functional impairment of the lung.
Radhakrishnamurthy
B
B
Department of Applied Health Sciences, Tulane University School of Public Health and Tropical Medicine, New Orleans, LA 70112.
D000818:Animals; D000990:Antithrombin III / Q000032:analysis; D002241:Carbohydrates / Q000032:analysis*; D002846:Chromatography, Affinity; D002851:Chromatography, High Pressure Liquid; D003238:Connective Tissue / Q000737:chemistry*; D004781:Environmental Exposure; D006025:Glycosaminoglycans / Q000032:analysis; D006497:Heparan Sulfate / Q000032:analysis; D008168:Lung / Q000737:chemistry* / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D010126:Ozone / Q000633:toxicity*; D011509:Proteoglycans / Q000032:analysis / Q000378:metabolism; D051381:Rats; D011916:Rats, Inbred F344
D000990:Antithrombin III; D002241:Carbohydrates; D006025:Glycosaminoglycans; D006497:Heparan Sulfate; D010126:Ozone; D011509:Proteoglycans