title: Regulation of hyaluronan secretion into rabbit synovial joints in vivo by protein kinase C.
abstract: Hyaluronan (HA) is important for joint cavitation, lubrication, volume regulation and synovial fluid drainage but little is known about the regulation of joint HA synthesis/secretion in vivo. We investigated whether HA secretion into joints in vivo can be regulated by protein kinase C (PKC). Secretion into the knee joint cavity of anaesthetised rabbits was measured over 6 h by washout and chromatography. Joints received intra-articular injections of Ringer vehicle (control) or an activator of classical PKC isoforms, phorbol-12-myristate-13-acetate (PMA), at 20-2000 ng ml(-1). The effects of PKC inhibition by bisindolylmaleimide (BIM) and protein synthesis inhibition by cycloheximide (CX) on basal and stimulated HA secretion were also studied. The endogenous HA mass, 181+/-8 microg (n=26, mean +/- S.E.M.), and basal secretion rate, 4.4+/-0.4 microg h(-1), indicated a turnover time of 41 h. Secretion rate showed a dose-dependent response to PMA (n=30), rising 5-fold to 21.7+/-5.0 microg h(-1) (n=5) at 2000 ng ml(-1) PMA (P<0.0001, one-way ANOVA). PMA-induced stimulation was partially suppressed by CX (HA secretion: 5.8+/-1.7 microg h(-1), n=8, P<0.01) and totally blocked by BIM (HA secretion: 3.2+/-0.6 microg h(-1), n=9, P<0.001). Basal HA secretion was unaffected by CX over 6 h (4.2+/-0.7 microg h(-1), n=8) but was reduced by 29 % by BIM (3.1+/-0.6 microg h(-1), n=10, P=0.03). It is concluded that: (1) PKC can stimulate HA secretion into joints in vivo through mechanisms involving protein synthesis de novo as well as phosphorylation; (2) basal HA secretion is only partially PKC dependent; and (3) hyaluronan synthase turnover time is >6 h in vivo, which is slower than in vitro (<2-3 h).
authors.affiliation: Department of Physiology, St George's Hospital Medical School, Cranmer Terrace, London SW17 0RE, UK.
authors.forename: C L
authors.initials: CL
authors.lastname: Anggiansah
authors.forename: D
authors.initials: D
authors.lastname: Scott
authors.forename: A
authors.initials: A
authors.lastname: Poli
authors.forename: P J
authors.initials: PJ
authors.lastname: Coleman
authors.forename: E
authors.initials: E
authors.lastname: Badrick
authors.forename: R M
authors.initials: RM
authors.lastname: Mason
authors.forename: J R
authors.initials: JR
authors.lastname: Levick
mesh_terms: D000818:Animals; D002851:Chromatography, High Pressure Liquid; D003513:Cycloheximide / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation / Q000187:drug effects / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006820:Hyaluronic Acid / Q000378:metabolism*; D007211:Indoles / Q000494:pharmacology; D007596:Joints / Q000473:pathology; D007700:Kinetics; D008301:Maleimides / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000502:physiology*; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D011817:Rabbits; D013582:Synovial Fluid / Q000378:metabolism*; D013585:Synovitis / Q000473:pathology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
chemical_list: D004791:Enzyme Inhibitors; D007211:Indoles; D008301:Maleimides; D011500:Protein Synthesis Inhibitors; D006820:Hyaluronic Acid; D003513:Cycloheximide; D011493:Protein Kinase C; C088060:bisindolylmaleimide; D013755:Tetradecanoylphorbol Acetate