Regulation of the secretory cycles of mucous and serous cells in the human bronchial gland.

Studies of the human bronchial gland in organ culture have allowed us to elucidate some of the factors controlling the synthesis and secretion of bronchial mucus. The secretory cycles of mucous and serous cells appear to differ, the former alternately accumulating and discharging secretory material, while in the latter synthesis and discharge occur simultaneously. Parasympathomimetic agents increase the secretory rate of mucous and serous cells by stimulating discharge, but have no effect on the rate of precursor incorporation into intracellular glycoproteins. Glycoprotein synthesis inhibitors reduce the incorporation of precursors into intracellular macromolecules but do not reduce the rate of discharge of preformed glycoproteins. The rate of glycoprotein synthesis appears to be greater in mucus-secreting cells of hypertrophied glands than of normals. Ouabain reduces the incorporation of glucose and threonine, but not glucosamine, into mucous and serous cells but has no effect on the rate of discharge. In hypertrophied glands, ouabain--sensitive threonine, but not glucose, transport appears to be increased. Exposure of rats to tobacco smoke causes an increase in the size of tracheal and laryngeal glands and in the secretory rate of mucous cells. The anti-inflammatory agent, phenylmethyloxadiazole, prevents both tobacco smoke-induced effects, presumably by reducing the secretory activity of mucous cells.