Tonin, an esteroprotease from rat submaxillary glands

Tonin is an enzyme found in the rat submaxillary glands which liberates angiotensin II from angiotensinogen, the Skeggs tetradecapeptide renin substrate, and angiotensin I. Tonin hydrolyzes benzoyl-arginine ethyl ester, benzoyl-arginine methyl ester, tosyl-arginine methyl ester, benzoyl-arginine p-nitroanilide and other small synthetic substrates at an optimum ph of 9.0. Tonin shows, however, a great specificity with respect to angiotensin I. Tonin is inhibited by diisopropyl fluorophosphate and phenylmethylsulfonyl fluoride at high concentrations (greater than 10(-2) M) and by soybean trypsin inhibitor and aprotinin. Tonin is thus an esteroprotease of the class of the serine protease with trypsin- and chymotrypsin-like activity. Tonin belongs to the same family of enzyme as glandular kallikrein and the gamma subunit of the nerve growth factor.     

Certain characteristic features of the lipolytic factor from rat submaxillary salivary glands

The aqueous extract of rat salivary submaxillary gland was found to contain three protein fractions activating the release of free fatty acids (FFA) and glycerol from rat epididymal adipose tissue in vitro. Physico-chemical investigations of these proteins demonstrated certain common features: all three fractions were albumins having a common isoelectric point, and their aqueous solutions absorbed light at the same wavelength. The use of lipolysis activators and inhibitors (theophylline, propranolol, insulin) for investigating their effects on FFA and glycerol release produced by these protein fractions explained the mechanism of the lipolytic action of the protein fractions from rat submaxillary glands.     

beta-Adrenergic and muscarinic cholinergic receptors in rat submaxillary glands. Effects of thyroidectomy.

Administration of triiodothyronine to thyroidectomized rats increased the density of beta-adrenergic receptors in rat submaxillary gland without significantly changing the density of muscarinic cholinergic receptors. Thus, thyroid hormone appears to regulate beta-adrenergic sensitivity in the rat salivary gland.     

Alteration of salt taste sensitivity by the neonatal removal of sublingual glands in the rat

1. Adult rats with the surgical removal of sublingual glands at their 10 days of age did not prefer NaCl solution of any concentration to water, whereas those with sham-operation or the removal of submandibular glands preferred 0.03 or 0.1 M NaCl to water. 2. Magnitudes of inhibition of chorda tympani responses to NaCl by the lingual treatment of 0.1 mM amiloride were greater in neonatally sublingual removed rats than in sham-operated or submandibular removed ones. 3. These results suggest that the removal of sublingual glands in neonatal period of the rat could increase the amount of the amiloride-sensitive Na receptor mechanism on the taste cell membrane in its adulthood.     

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

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 beta-galactosyltransferase (EC 2.4.1.22) and UDP-galactose:2-acetamido-2-deoxy-D-galactosaminyl-protein 3 beta-galactosyltransferase (no EC number), undergo tissue-specific change rather than changes induced by physiological stimulation of the salivary glands.