title: Inhibition of synthesis of rat parotid secretory proteoglycan in a gland slice system.
abstract: The chondroitin sulphate contained within the secretory granules of the rat parotid gland and its saliva was shown to be in the form of a proteoglycan by using inhibitors of proteoglycan synthesis in a gland slice system. Gland slices were incubated in either p-nitrophenyl-beta-D-xyloside or chlorate in the presence of both [3H]-leucine and [35S]-sulphate. The slices were next homogenized and either the 250 g supernatant fraction (for initial experiments) or secretory granule-containing fractions were isolated. Protein and proteoglycans of these fractions were precipitated in 10% trichloracetic acid (TCA), and glycosaminoglycans in cetylpyridinium chloride. [3H]-leucine and [35S]-sulphate were quantitated in each type of precipitate by scintillation counting. The results showed that 1 mM xyloside had no effect on protein or glycosaminoglycan synthesis but blocked incorporation of radiosulphate into TCA-precipitable material. Sixteen mM chlorate almost totally inhibited incorporation of radiosulphate into glycosaminoglycan and TCA-precipitable material. These findings demonstrate that the rat parotid secretory chondroitin sulphate is indeed a proteoglycan because its synthesis is blocked by the protein-core analogue acceptor, p-nitrophenyl-beta-D-xyloside. This system offers opportunities for exploring the functional role of chondroitin sulphate proteoglycan in this salivary gland.
authors.affiliation: Department of Oral Biology, School of Dentistry, University of Washington, Seattle 98195.
authors.forename: M R
authors.initials: MR
authors.lastname: Robinovitch
authors.forename: J M
authors.initials: JM
authors.lastname: Iversen
authors.forename: K T
authors.initials: KT
authors.lastname: Izutsu
mesh_terms: D000818:Animals; D002704:Chlorates / Q000008:administration & dosage / Q000494:pharmacology*; D002809:Chondroitin Sulfates / Q000037:antagonists & inhibitors* / Q000096:biosynthesis; D003594:Cytoplasmic Granules / Q000187:drug effects / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D006023:Glycoproteins / Q000096:biosynthesis; D006025:Glycosaminoglycans / Q000096:biosynthesis; D006027:Glycosides / Q000008:administration & dosage / Q000494:pharmacology*; D007930:Leucine / Q000378:metabolism; D008297:Male; D010306:Parotid Gland / Q000187:drug effects* / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D012471:Salivary Proteins and Peptides / Q000037:antagonists & inhibitors* / Q000096:biosynthesis; D013431:Sulfates / Q000378:metabolism; D013462:Sulfur Radioisotopes; D014316:Tritium
chemical_list: D002704:Chlorates; D006023:Glycoproteins; D006025:Glycosaminoglycans; D006027:Glycosides; D012471:Salivary Proteins and Peptides; D013431:Sulfates; D013462:Sulfur Radioisotopes; C010807:xylosides; D014316:Tritium; D002809:Chondroitin Sulfates; D007930:Leucine; C032706:sodium chlorate