Glycoprotein synthesis by the trachea.

Slices of rat trachea incubated with d-glucosamine-1-14C incorporated radioactivity into protein, that is, material insoluble in cold ethanol, cold and hot trichloroacetic acid and not extracted by lipid solvents. Incorporation was dose-dependent, occurred at an optimal pH of 8 and was decreased in the presence of glucose. A small amount of d-glucosamine-14C was metabolized to 14CO2. Compared to l-leucine-14C, the curve of glucosamine incorporation rose less steeply initially, and the ascending limb assumed a sigmoid shape. Puromycin inhibited incorporation of radioactivity from glucosamine by 44 per cent to 72 per cent and from leucine by more than 95 per cent. The microsomal fraction of tracheal homogenate had the highest specific activity of the subcellular fractions throughout a four-hour incubation. The alcohol-insoluble radioactive product was mostly resistant to hyaluronidase but was made soluble by Pronase®; treatment with neuraminidase, and acid hydrolysis yielded radioactive materials having the...