Development of the airway epithelium and submucosal glands in the pig lung: changes in epithelial glycoprotein profiles.

Glycoproteins in the normal airway surface epithelium and submucosal glands of 13 Large White pigs were studied from birth to adult life using alcian blue (AB) staining at pH 2.6 or at pH 1.0, with and without sialidase digestion, and by the combination of AB and PAS (AB/PAS) stains. Immediately after birth the percentage of cells producing acidic and neutral glycoproteins increased in both airway surface epithelium and submucosal glands. In the airway surface epithelium, the percentage of mucus-secreting cells producing sulphated glycoprotein increased with age, whereas in the submucosal glands the glycoproteins were mainly sulfated between birth and 3 days and sialylated between 3 days and adult life. The percentage of cells producing neutral glycoprotein in the airway surface epithelium increased during the first 24 h of life after which there was little change with age. In the submucosal glands, however, the greatest increase in the percentage of cells producing neutral glycoprotein occurred between 7 days and adult life. The rapid increase of intracellular glycoprotein production at birth and the presence of the same types of glycoprotein in the immature pig and mature human lung, suggest that the pig may be a useful model in which to study mechanisms and changes of glycoprotein synthesis and secretion during lung development.