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In this study, we attempted to clarify cytochemically whether or not transports of macromolecules being derived from tlood were controlled by synovial lining cells respectively. centered on the uptake of intravenously injected exogenous peroxidase by rat synovial lining cells in the temporomandibular joint (T.M.J.)Adult male Wistar rats weighing 300-400 g were anesthetized with pentobarbital sodium. Thirty mg of horseradish peroxidase** (HRP) (MW; about 40,000) dissolved in 0.6 ml of 0.9c NaCl was injected through the fensoral vein.Four animals were killed at 90 sec and 5, 15 and 60 inin after injection of HRP. The synovial lining was removed, and fixed for 4 hoturs irn 2.5% glutaraldehyde in 0.1 M cacodylate buffer (pH 7.4). After fixation, the tissuIe was washed in the same btuffer and then made into frozen sections about 40 gm thick.For the demiionstration of peroxidase activity, sections were incubated at room temperature for 30 rn in the 3.3'-diaminobenzidine (DAB) medium (J Histochem Cytochern 14: [291][292][293][294][295][296][297][298][299][300][301][302] 1966). As controls, some sections were incubated in the medium lacking II. 02 or DAB. After incubation, the swctions were )ostfixed in osmium tetroxide and processed for electron microscopy.The synovial lining of 0.9% NaCl-uininjected animals, or of those after the intravenouLs injection of 0.9%G NaCl, was likcwisc treated to detect endogenous peroxidase activity.When HRP was injected intravenously to * *Type 11, Sigma Cliemical Co., U.S.A.rats, type A cells were positive for HRP activity, while type B cells and fibroblasts were negative. Thus, a difference inIHRP incorporation by synovial lining cells was apparent.In the early stage (90 see and 5 min) of injection of HRP, its reaction product was found in membrane-bound vesicular and tubular structures within type A cells. Althotugh miost HRPpositive vesicles were sm-iooth, a small number of these vesicles were coated with bristle-like structures. A reaction product was also found in structures that seemed to be in the process of pinocytosis. Fifteen minutes after injection. HIRP-positive structuires founcl in type A cells outnu-imbered those which had been observed in the first few minutes after injection. In type A cells, most high accumulation of HRP-reaction prodduct was found 60 min after injection. Throughout the stage studied. HRP-reaction product was not detected in the extracellular space of synovial lining cells or within the articular cavity.No HIRP activity was detected when sections were incubated in the inediu-m lacking IH20-f or DAB. Endogenous peroxidase activity was not found in synovial lining cells taken from 0.9crtv NaCl-injected rat and from 0.9%,;S NaCluninjected rat, though it was detected in red blood cells due to the peroxidatic effect of hernoglobin.It is concluded that intravenou-sly injected HRP is incorporated into type A cells rather than type B cells by pinocytosis throuigh the cell membrane. Although the uptake of exogenous HRP of plant origin was carried ouit predom...

In the present paper, the effect of the occlusal changes on the rat temporomanidibular joint (TM]) synovial lining cells was cytochemically investigated. Twenty-four adult (nine-week-old) male Wistar rats were used as an experimental group. The left upper and lower molars of the rats were extracted. Food and water was supplied ad libitum. At intervals of one, two, three, four, five, eight, 12, and 16 wk following experimental procedures, the animals (three rats/period of study) were anesthetized, and 30 mg of horseradish peroxidase (HlRP) were injected through the femoral vein in order to examine the endocytotic activity of type A cells in synovial menmbrane. The rats were killed one h after injection of HIRP. The synovium of the left TMJ was removed and fixed in 2.57 glutaraldehyde (pH l7.4). The tissue was made into frozen sections about 40 gpmi thick. For the demonstration of the peroxidase activity, the tissue was incubated in 3,3'-diamiinobenzidine medium for 30 min (J Histochem Cytochem 14: 291-302, 1966). The sections were postfixed in osmium tetroxide and processed for electron Supported in part by a grant fromn Osaka Dental University i~~~~~i N JS 4 4microscopy. As a conitrol group, fifteen niale (nine-week-old) Wistar rats were used to avoid the aging factor. Animals were fed the same diet and water for two, three, four, eight, and 16 wk without surgical procedure. Animals (three rats corresponding to each feeding time) were provided for HRP techniique in the same manainer.Normal synovium from each control aniimal (from 11-week-old to 25 -week-old) indicated nearly the same findings as for the synovium one h after injection of HRP (J Detnt Res 56:1376Res 56: , 1977. The surface layer of the normal synovial tissue was occupied by predominant type A cells which were positive for HRI' activity. The number of HRP reaction products decreased in type A cells four or five wk after extraction. Type A cells also showed vacuolization in the cytoplasm five wk after the extraction of molars. Intercellular space was characterized by accumulation of collagen fibers. There were small amounts of HRP reaction products in type A cells eight and 12 wk after extraction. On the other hand, the vacuolization in type A cells subsequently increased in size and number. It is concluded that the TMJ disturbance of the rat caused by extraction of molars was followed by degenerative changes in type A cells, in which the uptake of HRI' decreased in accordance with the degree of degeneration. 4

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