Comparative developmental analysis of the parotid, submandibular and sublingual glands in the neonatal rat

Abstract

Analysis of the soluble protein fractions from the rat parotid, submandibular and sublingual glands by polyacrylamide-gel electrophoresis reveals similarities in overall patterns of protein synthesis at birth. Tissue-specific changes in protein and glycoprotein synthesis occur shortly after birth and again at the time of weaning, 21-28 days later. Incorporation of [3H]thymidine into DNA was at its highest after birth and gradually decreased in both the parotid and submandibular gland, whereas [3H]thymidine incorporation in the sublingual gland was low throughout the time of neonatal development. [14C]Leucine incorporation into total protein increased in all glands with age after birth, showing an accelerated rate 21-28 days later. Trichloroacetic acid/phosphotungstic acid-precipitable [3H]fucose in glycoproteins declined over the time of neonatal development in the parotid and submandibular gland, but its incorporation remained higher in the sublingual gland. alpha-Amylase (EC 3.2.1.1) in the salivary glands increased at the time of weaning, as judged by detectability in sodium dodecyl sulphate/polyacrylamide gels and by immune precipitation. Two membrane-bound enzymes, UDP-galactose:2-acetamido-2-deoxy-D-glucosamine 4 β-galactosyltransferase (EC 2.4.1.22) and UDP-galactose:2-acetamido-2-deoxy-D-galactosaminyl-protein 3 β-galactosyltransferase (no EC number), undergo tissue-specific change rather than changes induced by physiological stimulation of the salivary glands.