Quantitation of mucous glycoprotein removed from the respiratory tract of the rat by pulmonary lavage.

Mucous glycoprotein (MGP) hypersecretion is a cause of chronic pulmonary obstructive disease and is also a common response of the pulmonary airways to toxicant-induced injury. To examine the feasibility of employing pulmonary lavage to assess the airway MGP content of the rat, the MGP removed from the lungs of male Sprague-Dawley rats by three successive lavages with cold isotonic saline were solubilized with urea and mercaptoethanol, and were purified by ultrafiltration and Sepharose CL-6B gel chromatography. MGP, which elute with the void volume of this gel, were quantitated by their carbohydrate content. Initial studies revealed that succeeding lavages removed succeedingly less MGP, suggesting that some pool of MGP was being washed out by this procedure. In a second study, isoproterenol was administered by a regimen known to produce MGP hypersecretion in the rat as assessed by histologic criteria (100 mg/kg/day, sc, for 6 days). Lavage MGP content of isoproterenol-treated rats averaged 450 micrograms compared to 210 micrograms in vehicle-treated controls (p = 0.01). In summary, it is possible to purify and quantitate the MGP removed from the airways of the rat by pulmonary lavage and the amount of lavagable MGP is approximately doubled by isoproterenol, an agent known to induce the morphologic signs of mucous hypersecretion.