Enzymatic sulfation of triglucosyl monoalkylmonoacylglycerol in rat salivary glands

Tyrosylprotein sulfotransferase in rat submandibular salivary glands

1. The transfer of sulfate ester group from 3'-phosphoadenosine 5'-phosphosulfate (PAPS) to poly-(Glu6, Ala3, Tyr1) (EAY; Mr 47 kDa) in rat submandibular salivary gland has been investigated. The highest tyrosylprotein sulfotransferase activity was obtained in the Golgi-enriched fraction in the presence of 2 mM 5'AMP, 20 mM MnCl2 and 50 mM NaF at pH 6.2. 2. The apparent Km values for EAY and PAPS were 1.6 x 10(-6) and 1.9 x 10(-6) M, respectively. 3. Inclusion of NaCl, EDTA, NEM and DTT was inhibitory for the enzyme activity. The enzyme was 28 times less susceptible to 2,6-dichloro-4-nitrophenol inhibition than to phenol sulfotransferase inhibition. 4. This study is the first report characterizing a sulfotransferase activity specific for tyrosylprotein in rat submandibular salivary glands.

Adrenergic and cholinergic regulation of phospholipid release in sublingual salivary gland in vitro

1. The role of adrenergic and cholinergic mediators in the regulation of salivary phospholipid secretion was investigated using rat sublingual acinar cells maintained in the presence of [3H]choline. 2. The release of [3H]choline containing phospholipids was enhanced by beta-adrenergic agonist, isoproterenol to a greater extent than the cholinergic agonist, pilocarpine. 3. The effect of isoproterenol on phospholipid release was observed even after 5 min and by 30 min a 1.7-fold increase in secretion occurred, whereas pilocarpine evoked 1.2-fold increase by 30 min with no discernible effect in 5 min. The isoproterenol effect was blocked by alprenolol, and an inhibition of pilocarpine effect was observed with atropine. 4. In the absence of mediators, 82% of secreted labeled phospholipids were represented by phosphatidylcholine (PC), 4.3% by lysophosphatidylcholine (LPC) and 12.1% by sphingomyeline (Sph), those secreted in the presence of isoproterenol showed significantly lower (37%) content of LPC, while those secreted in response to pilocarpine were substantially richer in LPC (2.5 times) and Sph (27%), and contained less (17%) PC. 5. The results provide first evidence for the involvement of adrenergic and cholinergic mediators in the regulation of salivary phospholipid secretion.